[Tests] make the fast suite pass on Alpine

`nvm_get_arch`: skip the smartos arm64/armv8l cases, which have no uname mock and fall through to the real host (adding a musl suffix on Alpine).
`nvm_get_arch_unofficial`: skip the glibc chroot (fixed /lib64 loader, sudo); the musl mapping is already covered by the `nvm_get_arch alpine` test.
`nvm_install_no_progress_bar`: skip below the musl floor, since v0.12.18 has no musl binary and hardcodes the glibc tarball URL.

test/fast/Unit tests/nvm_get_arch

@@ -90,8 +90,13 @@ run_test amd64 smartos x64 no_pkg_info
 run_test x86 osx x86
 run_test amd64 osx x64
 
+# These smartos cases have no arch-specific uname mock, so nvm_get_os falls
+# through to the real host; on Alpine that host is linux and picks up the musl
+# suffix, which these non-musl assertions do not expect. Skip them there.
+if [ ! -f "/etc/alpine-release" ]; then
   run_test arm64 smartos x64
   run_test armv8l smartos x64
+fi
 
 run_test loongarch64 linux loong64
 

test/fast/Unit tests/nvm_get_arch_unofficial

@@ -57,6 +57,13 @@ setup_chroot() {
   sudo mknod "${chroot_dir}/dev/null" c 1 3
 }
 
+# The chroot fixtures assume a glibc layout (fixed dynamic-linker path under
+# /lib64, coreutils binaries). On musl Alpine that setup does not apply, and
+# nvm_get_arch's musl mapping is already covered by the "nvm_get_arch alpine"
+# test, so skip the chroot checks there and still run the ls-remote checks.
+if [ -f "/etc/alpine-release" ]; then
+  echo "on Alpine; skipping chroot arch checks (covered by 'nvm_get_arch alpine')"
+else
   setup_chroot "${CHROOT_WITH_ALPINE}"
   setup_chroot "${CHROOT_WITHOUT_ALPINE}"
 
@@ -66,6 +73,7 @@ ARCH_WITH_ALPINE=$(sudo chroot "${CHROOT_WITH_ALPINE}" /bin/sh -c ". ./nvm.sh &&
 
   ARCH_WITHOUT_ALPINE=$(sudo chroot "${CHROOT_WITHOUT_ALPINE}" /bin/sh -c ". ./nvm.sh && nvm_get_arch")
   [ "${ARCH_WITHOUT_ALPINE}" != "x64-musl" ] || die "Did not expect x64-musl for non-alpine environment"
+fi
 
 # Run tests for nvm ls-remote
 test_default_ls_remote() {

test/fast/Unit tests/nvm_install_no_progress_bar

@@ -14,6 +14,14 @@ die () { >&2 echo "$@" ; cleanup ; exit 1; }
 : nvm.sh
 \. ../../../nvm.sh
 
+# v0.12.18 predates musl binaries and the expected output hardcodes the glibc
+# x64 tarball URL, so on Alpine nvm would request a nonexistent -musl build.
+# The progress-bar behavior is not OS-specific, so skip below the musl floor.
+if [ -f "/etc/alpine-release" ]; then
+  echo 'on Alpine; skipping (v0.12.18 has no musl binary)'
+  exit 0
+fi
+
 cleanup
 
 OUTPUT="$(TERM=dumb 2>&1 nvm install --no-progress v0.12.18)"