Makefile: Make sure CROSS_COMPILE is set correctly

When testing a change to set the default compiler to clang for
dartmonkey, I encountered an error when building with
"make proj-bloonchipper":

ccache: error: execv of /opt/coreboot-sdk/bin/arm-eabi-clang failed: No
such file or directory

In this case the CC variable (defined in Makefile.toolchain as
"CC=$(CCACHE) $(CROSS_COMPILE)$(cc-name))" had CROSS_COMPILE set to
"/opt/coreboot-sdk/bin/arm-eabi-" (gcc toolchain) and cc-name set to
"clang", which is not correct.

The problem was that the Makefile has simply expanded variables
(https://www.gnu.org/software/make/manual/html_node/Flavors.html#Flavors)
that reference CC before the core/$(CORE)/build.mk is included (e.g.,
"_tsk_lst_ro" that uses CPP, which is defined as "CPP=$(CC) -E").

This change pulls the toolchain configuration out of
core/$(CORE)/build.mk into a separate core/$(CORE)/toolchain.mk file
that is included earlier in the top-level Makefile, which ensures that
CC is defined before it is used by the simply expanded variables.

BRANCH=none
BUG=b:172020503, b:234181908
TEST=make proj-bloonchipper -j
TEST=./util/compare_build.sh -b all -j 120
     => MATCH

Signed-off-by: Tom Hughes <tomhughes@chromium.org>
Change-Id: Ia41d2de61ee786df044d484c146d6970de183562
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3706036
Reviewed-by: Denis Brockus <dbrockus@chromium.org>

10 files changed, 53 insertions, 39 deletions

diff --git a/core/cortex-m/build.mk b/core/cortex-m/build.mk
index bcffe16e8d..04f8e45479 100644
--- a/core/cortex-m/build.mk
+++ b/core/cortex-m/build.mk
@@ -6,19 +6,6 @@
 # Cortex-M4 core OS files build
 #
 
-
-ifeq ($(cc-name),gcc)
-# coreboot sdk
-CROSS_COMPILE_ARM_DEFAULT:=/opt/coreboot-sdk/bin/arm-eabi-
-else
-# llvm sdk
-CROSS_COMPILE_ARM_DEFAULT:=armv7m-cros-eabi-
-endif
-
-$(call set-option,CROSS_COMPILE,\
-	$(CROSS_COMPILE_arm),\
-	$(CROSS_COMPILE_ARM_DEFAULT))
-
 # FPU compilation flags
 CFLAGS_FPU-$(CONFIG_FPU)=-mfloat-abi=hard
 ifeq ($(cc-name),gcc)
diff --git a/core/cortex-m/toolchain.mk b/core/cortex-m/toolchain.mk
new file mode 100644
index 0000000000..736d4c7562
--- /dev/null
+++ b/core/cortex-m/toolchain.mk
@@ -0,0 +1,15 @@
+# Copyright 2022 The ChromiumOS Authors.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+ifeq ($(cc-name),gcc)
+# coreboot sdk
+CROSS_COMPILE_ARM_DEFAULT:=/opt/coreboot-sdk/bin/arm-eabi-
+else
+# llvm sdk
+CROSS_COMPILE_ARM_DEFAULT:=armv7m-cros-eabi-
+endif
+
+$(call set-option,CROSS_COMPILE,\
+	$(CROSS_COMPILE_arm),\
+	$(CROSS_COMPILE_ARM_DEFAULT))
diff --git a/core/cortex-m0/build.mk b/core/cortex-m0/build.mk
index eab2a1eb1c..37ff34873b 100644
--- a/core/cortex-m0/build.mk
+++ b/core/cortex-m0/build.mk
@@ -6,18 +6,6 @@
 # Cortex-M0 core OS files build
 #
 
-ifeq ($(cc-name),gcc)
-# coreboot sdk
-CROSS_COMPILE_ARM_DEFAULT:=/opt/coreboot-sdk/bin/arm-eabi-
-else
-# llvm sdk
-CROSS_COMPILE_ARM_DEFAULT:=arm-none-eabi-
-endif
-
-$(call set-option,CROSS_COMPILE,\
-	$(CROSS_COMPILE_arm),\
-	$(CROSS_COMPILE_ARM_DEFAULT))
-
 # CPU specific compilation flags
 CFLAGS_CPU+=-mthumb
 ifeq ($(cc-name),clang)
diff --git a/core/cortex-m0/toolchain.mk b/core/cortex-m0/toolchain.mk
new file mode 100644
index 0000000000..390dd6a7f2
--- /dev/null
+++ b/core/cortex-m0/toolchain.mk
@@ -0,0 +1,15 @@
+# Copyright 2022 The ChromiumOS Authors.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+ifeq ($(cc-name),gcc)
+# coreboot sdk
+CROSS_COMPILE_ARM_DEFAULT:=/opt/coreboot-sdk/bin/arm-eabi-
+else
+# llvm sdk
+CROSS_COMPILE_ARM_DEFAULT:=arm-none-eabi-
+endif
+
+$(call set-option,CROSS_COMPILE,\
+	$(CROSS_COMPILE_arm),\
+	$(CROSS_COMPILE_ARM_DEFAULT))
diff --git a/core/minute-ia/build.mk b/core/minute-ia/build.mk
index b51512c16e..b32f8164ea 100644
--- a/core/minute-ia/build.mk
+++ b/core/minute-ia/build.mk
@@ -6,10 +6,6 @@
 # Minute-IA core build
 #
 
-# Select Minute-IA bare-metal toolchain
-$(call set-option,CROSS_COMPILE,$(CROSS_COMPILE_i386),\
-	/opt/coreboot-sdk/bin/i386-elf-)
-
 # FPU compilation flags
 CFLAGS_FPU-$(CONFIG_FPU)=
 
diff --git a/core/minute-ia/toolchain.mk b/core/minute-ia/toolchain.mk
new file mode 100644
index 0000000000..8fcfc28c78
--- /dev/null
+++ b/core/minute-ia/toolchain.mk
@@ -0,0 +1,7 @@
+# Copyright 2022 The ChromiumOS Authors.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Select Minute-IA bare-metal toolchain
+$(call set-option,CROSS_COMPILE,$(CROSS_COMPILE_i386),\
+	/opt/coreboot-sdk/bin/i386-elf-)
diff --git a/core/nds32/build.mk b/core/nds32/build.mk
index ddd65c680b..e500846c44 100644
--- a/core/nds32/build.mk
+++ b/core/nds32/build.mk
@@ -6,12 +6,6 @@
 # Andestar v3m architecture core OS files build
 #
 
-# Set coreboot-sdk as the default toolchain for nds32
-NDS32_DEFAULT_COMPILE=/opt/coreboot-sdk/bin/nds32le-elf-
-
-# Select Andes bare-metal toolchain
-$(call set-option,CROSS_COMPILE,$(CROSS_COMPILE_nds32),$(NDS32_DEFAULT_COMPILE))
-
 # CPU specific compilation flags
 CFLAGS_CPU+=-march=v3m -Os
 LDFLAGS_EXTRA+=-mrelax
diff --git a/core/nds32/toolchain.mk b/core/nds32/toolchain.mk
new file mode 100644
index 0000000000..3d685ef2b6
--- /dev/null
+++ b/core/nds32/toolchain.mk
@@ -0,0 +1,9 @@
+# Copyright 2022 The ChromiumOS Authors.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Set coreboot-sdk as the default toolchain for nds32
+NDS32_DEFAULT_COMPILE=/opt/coreboot-sdk/bin/nds32le-elf-
+
+# Select Andes bare-metal toolchain
+$(call set-option,CROSS_COMPILE,$(CROSS_COMPILE_nds32),$(NDS32_DEFAULT_COMPILE))
diff --git a/core/riscv-rv32i/build.mk b/core/riscv-rv32i/build.mk
index 7e5ce0e8a7..f558a91669 100644
--- a/core/riscv-rv32i/build.mk
+++ b/core/riscv-rv32i/build.mk
@@ -6,10 +6,6 @@
 # RISC-V core OS files build
 #
 
-# Select RISC-V bare-metal toolchain
-$(call set-option,CROSS_COMPILE,$(CROSS_COMPILE_riscv),\
-	/opt/coreboot-sdk/bin/riscv64-elf-)
-
 # Enable FPU extension if config option of FPU is enabled.
 _FPU_EXTENSION=$(if $(CONFIG_FPU),f,)
 # Enable the 'M' extension if config option of RISCV_EXTENSION_M is enabled.
diff --git a/core/riscv-rv32i/toolchain.mk b/core/riscv-rv32i/toolchain.mk
new file mode 100644
index 0000000000..dd45daf120
--- /dev/null
+++ b/core/riscv-rv32i/toolchain.mk
@@ -0,0 +1,7 @@
+# Copyright 2022 The ChromiumOS Authors.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Select RISC-V bare-metal toolchain
+$(call set-option,CROSS_COMPILE,$(CROSS_COMPILE_riscv),\
+	/opt/coreboot-sdk/bin/riscv64-elf-)