fix: add Z3 static lib search path to RUSTFLAGS for musl build

z3-sys build.rs only emits cargo:rustc-link-search when the
static-link-z3 feature is enabled. Since we build Z3 from source
without that feature, the linker never gets -L /usr/local/z3-static/lib.
Adding it via RUSTFLAGS ensures the linker can find libz3.a.

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

Author: AkiraTamai

.github/workflows/release.yml

@@ -75,6 +75,9 @@ jobs:
           sudo ninja install
           echo "Z3_SYS_Z3_HEADER=/usr/local/z3-static/include/z3.h" >> $GITHUB_ENV
           echo "Z3_SYS_Z3_LIB_DIR=/usr/local/z3-static/lib" >> $GITHUB_ENV
+          # z3-sys build.rs only emits rustc-link-search with static-link-z3 feature;
+          # we must add the search path manually via RUSTFLAGS
+          echo "RUSTFLAGS=-L /usr/local/z3-static/lib" >> $GITHUB_ENV
       - name: Install system dependencies (macOS)
         if: runner.os == 'macOS'
         run: |