Rollup merge of #47283 - malbarbo:musl-1.1.18, r=alexcrichton

Update musl to 1.1.18

According to http://www.musl-libc.org/download.html:

This release corrects regressions in glob() and armv4t build failure
introduced in the previous release, and includes an important bug fix
for posix_spawnp in the presence of a large PATH environment variable.

diff --cc src/ci/docker/scripts/musl.sh
Simple merge