move linker flags

Author: brianlball

ci/github-actions/setup.sh

@@ -126,16 +126,7 @@ else
         ulimit -a
         ulimit -n 4096
         ulimit -a
-        
-        if [[ "${INTEL}" == "false" ]]; then
-            # Ensure gmp exists for native gems (bigdecimal link step uses -lgmp)
-            brew install gmp
-
-            # Help the portable ruby toolchain find ARM Homebrew libs/headers
-            export CPPFLAGS="${CPPFLAGS:-} -I/opt/homebrew/include"
-            export LDFLAGS="${LDFLAGS:-} -L/opt/homebrew/lib"
-            export PKG_CONFIG_PATH="${PKG_CONFIG_PATH:-}:/opt/homebrew/lib/pkgconfig"
-        fi
+
     elif [ "${ImageOS}" == "ubuntu22" ]; then
         echo "Setting up Ubuntu for unit tests and Rubocop"
         # install pipe viewer to throttle printing logs to screen (not a big deal in linux, but it is in osx)
@@ -198,6 +189,19 @@ else
     # test openssl
     ruby ${GITHUB_WORKSPACE}/ci/github-actions/verify_openstudio.rb
 
+    if [[ "${ImageOS}" == "macos15" && "${INTEL}" == "false" ]]; then
+      brew list gmp >/dev/null 2>&1 || brew install gmp
+      BREW_PREFIX="$(brew --prefix)"
+      GMP_PREFIX="$(brew --prefix gmp 2>/dev/null || echo "${BREW_PREFIX}")"
+
+      export CPPFLAGS="-I${BREW_PREFIX}/include ${CPPFLAGS:-}"
+      export LDFLAGS="-L${BREW_PREFIX}/lib ${LDFLAGS:-}"
+      export PKG_CONFIG_PATH="${BREW_PREFIX}/lib/pkgconfig:${PKG_CONFIG_PATH:-}"
+
+      # (optional but helpful) force this one gem’s build to use gmp prefix
+      export BUNDLE_BUILD__BIGDECIMAL="--with-opt-dir=${GMP_PREFIX}"
+    fi
+
     ruby "${GITHUB_WORKSPACE}/bin/openstudio_meta" install_gems --with_test_develop --debug --verbose --use_cached_gems
     bundle -v
     # create dir for output files which will be generated in case of failure