fix(ci): set CXX for musl targets so z3 bundled cmake can find a C++ compiler

musl-tools only provides musl-gcc (C compiler wrapper), not musl-g++.
The z3 bundled cmake build needs a C++ compiler to compile z3 from
source. Use the system g++ since z3 exposes a C-linkage API and
libstdc++ is statically linked in the final musl binary.

Author: johntmyers

.github/workflows/release-dev.yml

@@ -220,6 +220,12 @@ jobs:
           sed -i -E '/^\[workspace\.package\]/,/^\[/{s/^version[[:space:]]*=[[:space:]]*".*"/version = "'"${{ needs.compute-versions.outputs.cargo_version }}"'"/}' Cargo.toml
 
       - name: Build ${{ matrix.target }}
+        env:
+          # musl-tools only provides musl-gcc (C); z3 bundled build needs a
+          # C++ compiler.  The system g++ works because z3's public API uses
+          # C linkage and libstdc++ is statically linked in the final binary.
+          CXX_aarch64_unknown_linux_musl: g++
+          CXX_x86_64_unknown_linux_musl: g++
         run: mise x -- cargo build --release --target ${{ matrix.target }} -p openshell-cli --features bundled-z3
 
       - name: sccache stats

.github/workflows/release-tag.yml

@@ -242,6 +242,9 @@ jobs:
           sed -i -E '/^\[workspace\.package\]/,/^\[/{s/^version[[:space:]]*=[[:space:]]*".*"/version = "'"${{ needs.compute-versions.outputs.cargo_version }}"'"/}' Cargo.toml
 
       - name: Build ${{ matrix.target }}
+        env:
+          CXX_aarch64_unknown_linux_musl: g++
+          CXX_x86_64_unknown_linux_musl: g++
         run: mise x -- cargo build --release --target ${{ matrix.target }} -p openshell-cli --features bundled-z3
 
       - name: sccache stats