Build wheels for musl-based linux (#167)

[pyproject.toml] Add musl back.

It is still faster to build wheels for both manylinux and musllinux than windows and macos

pyproject.toml

@@ -9,7 +9,7 @@ build-backend = "setuptools.build_meta"
 
 [tool.cibuildwheel]
 # only build for 64-bit
-skip = ["*-manylinux_i686", "*-musllinux*"]
+skip = ["*-manylinux_i686", "*-musllinux_i686"]
 
 test-requires = "pytest"
 test-command = "pytest {project}/tests"
@@ -32,3 +32,8 @@ before-test = "ccache --show-stats"
 [tool.cibuildwheel.linux.environment]
 CC = "/usr/lib64/ccache/gcc"
 CFLAGS = "-g0"
+
+[[tool.cibuildwheel.overrides]]
+select = "*-musllinux*"
+before-all = "apk add ccache"
+environment = {CC = "/usr/lib/ccache/bin/gcc"}