crossgcc: Preparations for building Ada frontend

As with most other languages, a pre-installed Ada toolchain is needed
to build gcc's Ada frontend. To support building with older host tool-
chains, the patch `gcc-5.2.0_gnat.patch` disables warnings for unknown
pragmas. Building has been tested with host gcc-4.9 and hopefully works
with newer versions, too.

For convenience, the gnattools (e.g. gnatmake etc.) will be build if
'ada' is specified as a target language.

Change-Id: Ia78c29d1aba2943de5238421a324cfff8eb08875
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: http://review.coreboot.org/11590
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

util/crossgcc/buildgcc

@@ -425,6 +425,11 @@ build_GCC() {
 		--with-pkgversion="coreboot toolchain v$CROSSGCC_VERSION $CROSSGCC_DATE" \
 		|| touch .failed
 	$MAKE $JOBS CFLAGS_FOR_BUILD="$HOSTCFLAGS" all-gcc || touch .failed
+
+	if [ "$(echo ${LANGUAGES} | grep -c '\<ada\>')" -gt 0 ]; then
+		$MAKE $JOBS CFLAGS_FOR_BUILD="$HOSTCFLAGS" -Cgcc/ cross-gnattools || touch .failed
+	fi
+
 	$MAKE install-gcc DESTDIR=$DESTDIR || touch .failed
 
 	if [ "$(echo $TARGETARCH | grep -c -- -mingw32)" -eq 0 ]; then

util/crossgcc/patches/gcc-5.2.0_gnat.patch

@@ -0,0 +1,11 @@
+--- gcc-5.2.0/gcc/ada/gcc-interface/Make-lang.in.bak	2015-08-24 16:23:25.004493665 +0200
++++ gcc-5.2.0/gcc/ada/gcc-interface/Make-lang.in	2015-08-24 17:53:52.496636113 +0200
+@@ -45,7 +45,7 @@
+ 
+ 
+ # Extra flags to pass to recursive makes.
+-COMMON_ADAFLAGS= -gnatpg
++COMMON_ADAFLAGS= -gnatpg -gnatwG
+ ifeq ($(TREECHECKING),)
+ CHECKING_ADAFLAGS=
+ else