[CI] test unstable abi in stage1

Since it seems so hard to get to stages 2 and 3

Author: jeremyd2019

.github/workflows/libcxx-build-and-test.yaml

@@ -44,6 +44,7 @@ jobs:
       matrix:
         config: [
           'frozen-cxx03-headers',
+          'generic-abi-unstable',
           'generic-cxx03',
           'generic-cxx26',
           'generic-modules'
@@ -54,6 +55,9 @@ jobs:
           - config: 'generic-gcc'
             cc: 'gcc-14'
             cxx: 'g++-14'
+          - config: 'generic-gcc-abi-unstable'
+            cc: 'gcc-14'
+            cxx: 'g++-14'
     steps:
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
       - name: ${{ matrix.config }}.${{ matrix.cxx }}

libcxx/test/libcxx/containers/sequences/deque/incomplete.pass.cpp

@@ -11,7 +11,7 @@
 // deque()
 // deque::iterator()
 
-// ADDITIONAL_COMPILE_FLAGS: -Wno-macro-redefined -D_LIBCPP_ABI_INCOMPLETE_TYPES_IN_DEQUE
+// ADDITIONAL_COMPILE_FLAGS: -Wno-error -Wno-macro-redefined -D_LIBCPP_ABI_INCOMPLETE_TYPES_IN_DEQUE
 
 #include <deque>
 #include <cassert>

libcxx/utils/ci/run-buildbot

@@ -353,6 +353,14 @@ generic-gcc-cxx11)
                    -DLIBUNWIND_ENABLE_WERROR=NO
     check-runtimes
 ;;
+generic-gcc-abi-unstable)
+    clean
+    generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-abi-unstable.cmake" \
+                   -DLIBCXX_ENABLE_WERROR=NO \
+                   -DLIBCXXABI_ENABLE_WERROR=NO \
+                   -DLIBUNWIND_ENABLE_WERROR=NO
+    check-runtimes
+;;
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