FS-8623: fix sun studio build errors building libvpx

Makefile.am

@@ -533,7 +533,7 @@ libs/libzrtp/libzrtp.a:
 	cd libs/libzrtp && $(MAKE)
 
 libs/libvpx/Makefile:
-	cd libs/libvpx && CC=$(CC) CXX=$(CXX) CFLAGS="$(CFLAGS)" CXXFLAGS="$(CXXFLAGS)" LDFLAGS="$(LDFLAGS)" ./configure --enable-pic --disable-docs --disable-examples --disable-install-bins --disable-install-srcs --disable-unit-tests --extra-cflags="-fvisibility=hidden"
+	cd libs/libvpx && CC="$(CC)" CXX="$(CXX)" CFLAGS="$(CFLAGS)" CXXFLAGS="$(CXXFLAGS)" LDFLAGS="$(LDFLAGS)" ./configure --enable-pic --disable-docs --disable-examples --disable-install-bins --disable-install-srcs --disable-unit-tests --extra-cflags="$(VISIBILITY_FLAG)"
 
 libs/libvpx/libvpx.a: libs/libvpx/Makefile
 	@cd libs/libvpx && $(MAKE)

configure.ac

@@ -451,6 +451,16 @@ if test "${enable_address_sanitizer}" = "yes"; then
 fi
 
 
+case "${ax_cv_c_compiler_vendor}" in
+sun)
+	VISIBILITY_FLAG=-xldscope=hidden
+;;
+*)
+	VISIBILITY_FLAG=-fvisibility=hidden
+;;
+esac
+AC_SUBST(VISIBILITY_FLAG)
+
 #
 # gcc visibility cflag checks
 #

libs/libvpx/libs.mk

@@ -107,7 +107,7 @@ ifeq ($(CONFIG_VP9_DECODER),yes)
 endif
 
 VP9_PREFIX=vp9/
-$(BUILD_PFX)$(VP9_PREFIX)%.c.o: CFLAGS += -Wextra
+$(BUILD_PFX)$(VP9_PREFIX)%.c.o:
 
 #  VP10 make file
 ifeq ($(CONFIG_VP10),yes)
@@ -141,7 +141,7 @@ ifeq ($(CONFIG_VP10_DECODER),yes)
 endif
 
 VP10_PREFIX=vp10/
-$(BUILD_PFX)$(VP10_PREFIX)%.c.o: CFLAGS += -Wextra
+$(BUILD_PFX)$(VP10_PREFIX)%.c.o:
 
 ifeq ($(CONFIG_ENCODERS),yes)
   CODEC_DOC_SECTIONS += encoder