[Buildroot] [PATCH v2] infra/ccache: avoid color diagnostics with GCC older than v4.9

[Carlos Santos]

Ensure that the GCC_COLORS environment variable is empty when calling
ccache. When GCC_COLORS is set, ccache passes '-fdiagnostics-color' to
GCC but this flag requires GCC v4.9 or later. Older versions complain
about the unrecognized command line option.

That behavior is hard-coded in ccache; we would need a patch to either
make it optional or disable it at all. Notice also that the problem is
not detectable in the autobuilders because they redirect the output to
files/pipes and ccache adds the offending flag only when stderr is a
terminal.

Signed-off-by: Carlos Santos <casantos at datacom.ind.br>
---
Changes v1->v2
  Fix indentation, use positive logic and improve the commit message,
  acording to comments from Thomas Petazzoni and Yann E. MORIN.

Signed-off-by: Carlos Santos <casantos at datacom.ind.br>
---
 package/Makefile.in | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/package/Makefile.in b/package/Makefile.in
index 4a3eb26..e5e595a 100644
--- a/package/Makefile.in
+++ b/package/Makefile.in
@@ -236,6 +236,13 @@ export PERL5LIB=$(HOST_DIR)/usr/lib/perl
 
 TARGET_MAKE_ENV = PATH=$(BR_PATH)
 
+# When GCC_COLORS is set, ccache passes '-fdiagnostics-color' to GCC but
+# this flag requires GCC v4.9 or later. Older versions fail, complaining
+# about unrecognized command line option.
+ifeq ($(BR2_TOOLCHAIN_GCC_AT_LEAST_4_9),)
+TARGET_MAKE_ENV += GCC_COLORS=""
+endif
+
 TARGET_CONFIGURE_OPTS = \
 	$(TARGET_MAKE_ENV) \
 	AR="$(TARGET_AR)" \
@@ -285,6 +292,11 @@ HOST_MAKE_ENV = \
 	PKG_CONFIG_ALLOW_SYSTEM_LIBS=1 \
 	PKG_CONFIG_LIBDIR="$(HOST_DIR)/usr/lib/pkgconfig:$(HOST_DIR)/usr/share/pkgconfig"
 
+# Prevent ccache from passing '-fdiagnostics-color' (see above).
+ifeq ($(BR2_HOST_GCC_AT_LEAST_4_9),)
+HOST_MAKE_ENV += GCC_COLORS=""
+endif
+
 HOST_CONFIGURE_OPTS = \
 	$(HOST_MAKE_ENV) \
 	AR="$(HOSTAR)" \
-- 
2.7.4