Fix gn compilation on mac with Xcode 11.4

Update to Xcode 11.4 introduces new weak symbol
which breaks gn linking with:

Undefined symbols for architecture x86_64:
"___darwin_check_fd_set_overflow"

This symbol is declared by FD_SET macros referenced in exec_process.c
and mark for weak linking, resulting object file has undefined
weak symbol:

(undefined) weak external ___darwin_check_fd_set_overflow

Unfortunately during linking this is not handled properly without
'isysroot' parameter passed to linker. Fix it in gn build script.

Change-Id: Ibb4c38aad098da1e119253cd89eba0216a921164
Reviewed-by: Michael Brüning <michael.bruning@qt.io>
(cherry picked from commit d5c4b6230b7f915f6e044e230c0c575249938400)
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

1 files changed, 2 insertions, 0 deletions

diff --git a/gn/build/gen.py b/gn/build/gen.py
index c6d2a6c1e4d..6df3c71387e 100755
--- a/gn/build/gen.py
+++ b/gn/build/gen.py
@@ -360,6 +360,8 @@ def WriteGNNinja(path, platform, host, options):
       ldflags.append('-O3')
       if platform.is_darwin() and options.isysroot:
         cflags.append('-isysroot ' +  options.isysroot)
+        ldflags.append('-isysroot ' +  options.isysroot)
+
       # Use -fdata-sections and -ffunction-sections to place each function
       # or data item into its own section so --gc-sections can eliminate any
       # unused functions and data items.