Isolate build temp dirs to prevent Cray compiler conflicts

Set per-build TMPDIR so concurrent Cray Fortran compilations on the
login node don't share temp files, which caused optcg segfaults on
m_phase_change.fpp.f90 during frontier gpu acc builds.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: sbryngelson

.github/scripts/run_frontier_all_benchmarks.sh

@@ -87,6 +87,9 @@ for i in "${!configs[@]}"; do
     echo "  Starting: $version $cluster $device $interface"
     (
         cd "$dir"
+        # Give each build its own temp dir to avoid Cray compiler conflicts
+        export TMPDIR="$(pwd)/.tmp-build"
+        mkdir -p "$TMPDIR"
         bash .github/workflows/${cluster}/build.sh "$device" "$interface" bench
     ) > "$log" 2>&1 &
     build_pids[$i]=$!

.github/scripts/run_frontier_all_tests.sh

@@ -92,6 +92,9 @@ for i in "${!configs[@]}"; do
     echo "  Starting: $cluster $device $interface"
     (
         cd "$dir"
+        # Give each build its own temp dir to avoid Cray compiler conflicts
+        export TMPDIR="$(pwd)/.tmp-build"
+        mkdir -p "$TMPDIR"
         bash .github/workflows/${cluster}/build.sh "$device" "$interface"
     ) > "$log" 2>&1 &
     build_pids[$i]=$!