ci: add Alpine (musl + GCC + SIMDE_NO_NATIVE) to Cirrus CI

Add a Cirrus CI task that builds and tests SIMDE on Alpine Linux (musl
libc) with GCC and SIMDE_NO_NATIVE disabled.

This combination catches link errors caused by __builtin_roundeven being
lowered to a roundeven() libm call on GCC 10+: musl lacks roundeven()
(C23), so the linker error surfaces immediately. SIMDE_NO_NATIVE ensures
the scalar path is taken even on x86-64 with SSE4.1, preventing GCC from
inlining the builtin as a ROUNDSD instruction and masking the issue.

Suggested during review of #1398.

Author: jkkim0724

.cirrus.yml

@@ -1,6 +1,23 @@
 container:
   image: debian:trixie-slim
 
+task:
+  name: Alpine (musl + GCC + SIMDE_NO_NATIVE)
+  skip: $BRANCH == "master" || ($BRANCH != 'ci/cirrus' && $BRANCH =~ '^ci/.+')
+  container:
+    image: alpine:latest
+  env:
+    CC: gcc
+    CXX: g++
+  install_dependencies_script:
+    - apk add --no-cache build-base meson ninja python3
+  configure_script:
+    - meson setup build -Dc_args="-DSIMDE_NO_NATIVE -Wextra -Werror" -Dcpp_args="-DSIMDE_NO_NATIVE -Wextra -Werror"
+  build_script:
+    - ninja -C build -v -j 3
+  test_script:
+    - ninja -C build -v test
+
 task:
   name: Sanitizers
   skip: $BRANCH == "master" || ($BRANCH != 'ci/cirrus' && $BRANCH =~ '^ci/.+')