GNUmakefile: shrink TinyGo binaries on Linux

.github/workflows/linux.yml

@@ -26,7 +26,7 @@ jobs:
         # tar: needed for actions/cache@v4
         # git+openssh: needed for checkout (I think?)
         # ruby: needed to install fpm
-        run: apk add tar git openssh make g++ ruby-dev
+        run: apk add tar git openssh make g++ ruby-dev mold
       - name: Work around CVE-2022-24765
         # We're not on a multi-user machine, so this is safe.
         run: git config --global --add safe.directory "$GITHUB_WORKSPACE"
@@ -73,7 +73,7 @@ jobs:
         uses: actions/cache/restore@v4
         id: cache-llvm-build
         with:
-          key: llvm-build-19-linux-alpine-v1
+          key: llvm-build-19-linux-alpine-v2
           path: llvm-build
       - name: Build LLVM
         if: steps.cache-llvm-build.outputs.cache-hit != 'true'
@@ -222,7 +222,7 @@ jobs:
         uses: actions/cache/restore@v4
         id: cache-llvm-build
         with:
-          key: llvm-build-19-linux-asserts-v1
+          key: llvm-build-19-linux-asserts-v2
           path: llvm-build
       - name: Build LLVM
         if: steps.cache-llvm-build.outputs.cache-hit != 'true'
@@ -329,7 +329,7 @@ jobs:
         uses: actions/cache/restore@v4
         id: cache-llvm-build
         with:
-          key: llvm-build-19-linux-${{ matrix.goarch }}-v3
+          key: llvm-build-19-linux-${{ matrix.goarch }}-v4
           path: llvm-build
       - name: Build LLVM
         if: steps.cache-llvm-build.outputs.cache-hit != 'true'

GNUmakefile

@@ -79,6 +79,26 @@ ifeq (1, $(STATIC))
     BINARYEN_OPTION += -DCMAKE_CXX_FLAGS="-static" -DCMAKE_C_FLAGS="-static"
 endif
 
+# Optimize the binary size for Linux.
+# These flags may work on other platforms, but have only been tested on Linux.
+ifeq ($(uname),Linux)
+    HAS_MOLD := $(shell command -v ld.mold 2> /dev/null)
+    HAS_LLD := $(shell command -v ld.lld 2> /dev/null)
+    LLVM_CFLAGS := -ffunction-sections -fdata-sections -fvisibility=hidden
+    LLVM_LDFLAGS := -Wl,--gc-sections
+    ifneq ($(HAS_MOLD),)
+        # Mold might be slightly faster.
+        LLVM_LDFLAGS += -fuse-ld=mold -Wl,--icf=all
+    else ifneq ($(HAS_LLD),)
+        # LLD is more commonly available.
+        LLVM_LDFLAGS += -fuse-ld=lld -Wl,--icf=all
+    endif
+    LLVM_OPTION += \
+        -DCMAKE_C_FLAGS="$(LLVM_CFLAGS)" \
+        -DCMAKE_CXX_FLAGS="$(LLVM_CFLAGS)"
+    CGO_LDFLAGS += $(LLVM_LDFLAGS)
+endif
+
 # Cross compiling support.
 ifneq ($(CROSS),)
     CC = $(CROSS)-gcc