Add BUILD_DPH variable to GHC build-system

Now that the `libraries/dph` submodule is checked out always we need
a different way to disable building DPH to save compile-time while
developing GHC.

This commit adds a new YES/NO Make variable `BUILD_DPH` that can be used
inside mk/build.mk to control whether to build libraries/dph or not.
The default setting is `BUILD_DPH=YES` (via `mk/config.mk.in`).

This also changes `validate`'s flag `--no-dph` to explicitly disable DPH
for the current validation run.

Signed-off-by: Herbert Valerio Riedel <hvr@gnu.org>

Test Plan: successful validates with `--fast --no-dph`

Differential Revision: https://phabricator.haskell.org/D31

1 files changed, 10 insertions, 3 deletions

diff --git a/validate b/validate
index 889c0e83a9..cabb86c7d3 100755
--- a/validate
+++ b/validate
@@ -22,9 +22,10 @@ Flags:
   --fast            Omit dyn way, omit binary distribution
   --slow            Build stage2 with -DDEBUG.
                     2008-07-01: 14% slower than the default.
-  --no-dph:         Skip requiring libraries/dph. In --slow mode, these tests
-                    can take a substantial amount of time, and on some platforms
-                    with broken linkers, we don't want to try compiling it.
+  --no-dph:         Skip building libraries/dph and running associated tests.
+                    In --slow mode, these tests can take a substantial amount
+                    of time, and on some platforms with broken linkers, we
+                    don't want to try compiling it.
   --help            shows this usage help.
 
   Set environment variable 'CPUS' to number of cores, to exploit
@@ -135,6 +136,12 @@ echo "Validating=YES"       >  mk/are-validating.mk
 echo "ValidateSpeed=$speed" >> mk/are-validating.mk
 echo "ValidateHpc=$hpc"     >> mk/are-validating.mk
 
+if [ $skip_dph -eq 1 ]; then
+    echo "BUILD_DPH=NO"     >> mk/are-validating.mk
+else
+    echo "BUILD_DPH=YES"    >> mk/are-validating.mk
+fi
+
 $make -j$threads
 # For a "debug make", add "--debug=b --debug=m"