[openwrt/openwrt] scripts: ext-toolchain: add support for musl

[LEDE Commits]

ansuel pushed a commit to openwrt/openwrt.git, branch openwrt-21.02:
https://git.openwrt.org/fd90eed40ce6828a1bbd11d1a394e7c6368d0577

commit fd90eed40ce6828a1bbd11d1a394e7c6368d0577
Author: Christian Marangi <ansuelsmth at gmail.com>
AuthorDate: Sun Jul 17 17:56:59 2022 +0200

    scripts: ext-toolchain: add support for musl
    
    Openwrt now supports only glibc and musl. Add support for musl and
    rework the libc check to handle the new config flags and correctly
    compile package basend on that.
    
    Signed-off-by: Christian Marangi <ansuelsmth at gmail.com>
    (cherry picked from commit 7be01fe13b4517e5edb8a4818f437d60144cdcb4)
---
 scripts/ext-toolchain.sh | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/scripts/ext-toolchain.sh b/scripts/ext-toolchain.sh
index 1f8eca3076..fe1024c18e 100755
--- a/scripts/ext-toolchain.sh
+++ b/scripts/ext-toolchain.sh
@@ -369,8 +369,18 @@ print_config() {
 	echo "CONFIG_TOOLCHAIN_PREFIX=\"$prefix\"" >> "$config"
 	echo "CONFIG_TARGET_NAME=\"$target\"" >> "$config"
 
-	if [ "$LIBC_TYPE" != glibc ]; then
-		echo "CONFIG_TOOLCHAIN_LIBC=\"$LIBC_TYPE\"" >> "$config"
+	if [ -f "$config" ]; then
+		sed -i '/CONFIG_EXTERNAL_TOOLCHAIN_LIBC_USE_MUSL/d' "$config"
+		sed -i '/CONFIG_EXTERNAL_TOOLCHAIN_LIBC_USE_GLIBC/d' "$config"
+	fi
+
+	if [ "$LIBC_TYPE" == glibc ]; then
+		echo "CONFIG_EXTERNAL_TOOLCHAIN_LIBC_USE_GLIBC=y" >> "$config"
+	elif [ "$LIBC_TYPE" == musl ]; then
+		echo "CONFIG_EXTERNAL_TOOLCHAIN_LIBC_USE_MUSL=y" >> "$config"
+	else
+		echo "Can't detect LIBC type. Aborting!" >&2
+		return 1
 	fi
 
 	local lib