autoconf: Add gcc search patch to MKDEP_OPTIONS to eliminate warnings.

Also, use -include to avoid error message when make initially fails to
include the non-existent depend file.

configs/autoconf.in

@@ -34,7 +34,7 @@ ASM_API = @ASM_API@
 MAKE = @MAKE@
 MKLIB_OPTIONS = @MKLIB_OPTIONS@
 MKDEP = @MKDEP@
-MKDEP_OPTIONS = -fdepend
+MKDEP_OPTIONS = @MKDEP_OPTIONS@
 INSTALL = $(TOP)/bin/minstall
 
 # Python and flags (generally only needed by the developers)

configure.ac

@@ -30,6 +30,15 @@ AC_PATH_PROG(MAKE, make)
 AC_PATH_PROG(MKDEP, makedepend)
 AC_PATH_PROG(SED, sed)
 
+dnl Ask gcc where it's keeping its secret headers
+if test "x$GCC" = xyes; then
+    GCC_PATH=$(gcc -print-search-dirs | sed -ne 's/install: //p')
+    MKDEP_OPTIONS="-fdepend -I${GCC_PATH}include"
+else
+    MKDEP_OPTIONS=-fdepend
+fi
+AC_SUBST(MKDEP_OPTIONS)
+
 dnl Make sure the pkg-config macros are defined
 m4_ifdef([PKG_PROG_PKG_CONFIG],,[
     AC_MSG_ERROR([The pkg-config autoconf macros are not defined.

src/glx/x11/Makefile

@@ -89,4 +89,4 @@ clean:
 	-rm -f *.o *~
 	-rm -f depend
 
-include depend
+-include depend

src/mesa/Makefile

@@ -197,4 +197,4 @@ clean:
 	(cd x86-64 && $(MAKE) clean)
 
 
-include depend
+-include depend

src/mesa/drivers/dri/Makefile.template

@@ -80,7 +80,7 @@ $(TOP)/$(LIB_DIR)/$(LIBNAME): $(LIBNAME)
 depend: $(C_SOURCES) $(ASM_SOURCES) $(SYMLINKS)
 	touch depend
 	$(MKDEP) $(MKDEP_OPTIONS) $(DRIVER_DEFINES) $(INCLUDES) $(C_SOURCES) \
-		$(ASM_SOURCES) 2>&1 /dev/null
+		$(ASM_SOURCES)
 
 
 # Emacs tags
@@ -99,4 +99,4 @@ install: $(LIBNAME)
 	$(INSTALL) -m 755 $(LIBNAME) $(DESTDIR)$(DRI_DRIVER_INSTALL_DIR)
 
 
-include depend
+-include depend