Only do LTO for publish builds to allow for one run to finish quickly

This helps give faster feedbacks when something broke.

Author: ychin

.github/workflows/ci-macvim.yaml

@@ -137,6 +137,12 @@ jobs:
             sed -i.bak -f ci/config.mk.clang-12.sed src/auto/config.mk
           fi
 
+          if ${{ matrix.publish == true }}; then
+            # Only do link-time optimizations for publish builds, so the other
+            # ones can still finish quickly to give quick feedbacks.
+            sed -i.bak -f ci/config.mk.lto.sed src/auto/config.mk
+          fi
+
       - name: Modify configure result
         if: matrix.publish
         run: |

ci/config.mk.lto.sed

@@ -0,0 +1,3 @@
+# Add link-time optimization for even better performance
+/^CFLAGS[[:blank:]]*=/s/$/ -flto/
+/^LDFLAGS[[:blank:]]*=/s/$/ -flto/