scripts/ext-toolchain: implement external GCC version detection

Some package may needs to enable compatibility option based on the GCC
version.

Currently the GCC version is set based on the default value and doesn't
actually reflect the real value provided by the external toolchain if
used.

Fix this by correctly detecting the GCC version in the external
toolchain and set the correct value in CONFIG_GCC_VERSION.

A new option is added in menuconfig to manually set the GCC version if
needed.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>

scripts/ext-toolchain.sh

@@ -27,6 +27,7 @@ CFLAGS=""
 TOOLCHAIN="."
 
 LIBC_TYPE=""
+GCC_VERSION=""
 
 
 # Library specs
@@ -199,6 +200,19 @@ find_bins() {
 	return 1
 }
 
+find_gcc_version() {
+	if [ -f $TOOLCHAIN/info.mk ]; then
+		GCC_VERSION=$(grep GCC_VERSION $TOOLCHAIN/info.mk | sed 's/GCC_VERSION=//')
+		return 0
+	fi
+
+	echo "Warning! Can't find info.mk, trying to detect with alternative way."
+
+	# Very fragile detection
+	GCC_VERSION=$(find $TOOLCHAIN/bin | grep -oE "gcc-[0-9]+\.[0-9]+\.[0-9]+$" | \
+		head -1 | sed 's/gcc-//')
+}
+
 
 wrap_bin_cc() {
 	local out="$1"
@@ -383,6 +397,13 @@ print_config() {
 		return 1
 	fi
 
+	if [ -n "$GCC_VERSION" ]; then
+		echo "CONFIG_EXTERNAL_GCC_VERSION=\"$GCC_VERSION\"" >> "$config"
+	else
+		echo "Can't detect GCC version. Aborting!" >&2
+		return 1
+	fi
+
 	local lib
 	for lib in C RT PTHREAD GCC STDCPP SSP GFORTRAN GOMP; do
 		local file
@@ -564,6 +585,7 @@ while [ -n "$1" ]; do
 		--config)
 			if probe_cc; then
 				probe_libc
+				find_gcc_version
 				print_config "$1"
 				exit $?
 			fi