builds: Add macOS CI

Author: michaelforney

.github/workflows/build.yml

@@ -0,0 +1,25 @@
+name: build
+on: [push]
+jobs:
+  build:
+    strategy:
+      matrix:
+        os: [macos-latest, macos-15-intel, macos-26-intel]
+        include:
+        - os: macos-latest
+          config: --host=aarch64-apple-darwin
+    runs-on: ${{ matrix.os }}
+    steps:
+    - uses: actions/checkout@v6
+    - name: qbe
+      run: |
+        git clone git://c9x.me/qbe.git
+        make -C qbe install
+    - name: setup
+      run: sudo patch -d "$(xcrun --show-sdk-path)" -i "$PWD/.github/workflows/macos.diff"
+    - name: build
+      run: ./configure ${{ matrix.config }} && make
+    - name: test
+      run: make check
+    - name: bootstrap
+      run: make bootstrap

.github/workflows/macos.diff

@@ -0,0 +1,14 @@
+--- usr/include/i386/_types.h.orig	2026-04-25 12:55:44
++++ usr/include/i386/_types.h	2026-04-25 12:59:28
+@@ -115,10 +115,8 @@
+ 
+ #if USE_CLANG_TYPES
+ typedef va_list                 __darwin_va_list;       /* va_list */
+-#elif (__GNUC__ > 2)
+-typedef __builtin_va_list       __darwin_va_list;       /* va_list */
+ #else
+-typedef void *                  __darwin_va_list;       /* va_list */
++typedef __builtin_va_list       __darwin_va_list;       /* va_list */
+ #endif
+ 
+ #if USE_CLANG_TYPES