configure: Test for -Wno-initializer-overrides

Clang has "-Wno-initializer-overrides", while gcc has
"-Wno-override-init". Quiets a lot of warnings with clang.

Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>
diff --git a/configure.ac b/configure.ac
index 50876b0..ac64a38 100644
--- a/configure.ac
+++ b/configure.ac
@@ -339,6 +339,10 @@
 AC_SUBST([VISIBILITY_CFLAGS])
 AC_SUBST([VISIBILITY_CXXFLAGS])
 
+AX_CHECK_COMPILE_FLAG([-Wno-override-init],                    [WNO_OVERRIDE_INIT="-Wno-override-init"])         # gcc
+AX_CHECK_COMPILE_FLAG([-Wno-initializer-overrides],            [WNO_OVERRIDE_INIT="-Wno-initializer-overrides"]) # clang
+AC_SUBST([WNO_OVERRIDE_INIT])
+
 dnl
 dnl Optional flags, check for compiler support
 dnl
diff --git a/src/intel/Makefile.am b/src/intel/Makefile.am
index 9946f67..a34e301 100644
--- a/src/intel/Makefile.am
+++ b/src/intel/Makefile.am
@@ -44,7 +44,7 @@
 
 AM_CFLAGS = \
 	$(VISIBILITY_CFLAGS) \
-	-Wno-override-init
+	$(WNO_OVERRIDE_INIT)
 
 MKDIR_GEN = $(AM_V_at)$(MKDIR_P) $(@D)
 PYTHON_GEN = $(AM_V_GEN)$(PYTHON2) $(PYTHON_FLAGS)