Add musl libc submodule

Since musl is already incorporated into the build system (see for
example configure.ac, Makefile.in), this patch adds a submodule for
musl based on the current v1.2.2 release.
The GitHub Actions configurations have also been updated to include
the musl based toolchain.

Signed-off-by: Florian Hofhammer <florian.hofhammer@fhofhammer.de>

1 files changed, 0 insertions, 0 deletions

diff --git a/musl b/musl
new file mode 160000
+Subproject 85e0e3519655220688e757b9d5bfd314923548b