Add compilers using musl-gcc: 4.01.0+musl, 4.01.0+musl+static

Requires musl-gcc to be installed (apt-get install musl-tools on Debian).
Merge pull request #2025 from edwintorok/musl-gcc

Add compilers using musl-gcc: 4.01.0+musl, 4.01.0+musl+static