Allow emcc build and validate in CI

.github/workflows/main.yml

@@ -58,13 +58,35 @@ jobs:
       uses: rlalik/setup-cpp-compiler@master
       with:
         compiler: ${{ matrix.compiler }}
+    - name: Setup emsdk
+      uses: mymindstorm/setup-emsdk@v14
+      with:
+        version: 3.1.51
+        actions-cache-folder: 'emsdk-cache'
     - name: fetch artifact first to reduce HTTP requests
       env:
         CC: ${{ steps.install_cc.outputs.cc }}
       run: |
             make artifact
             make ENABLE_SYSTEM=1 artifact
             make ENABLE_ARCH_TEST=1 artifact
+            # Hack Cloudflare 403 Forbidden on GitHub Runner for Doom artifact download
+            wget --header="User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:122.0) Gecko/20100101 Firefox/122.0" \
+                 --header="Referer: https://www.doomworld.com/" \
+                 --header="Accept-Language: en-US,en;q=0.9" \
+                 -O build/shareware_doom_iwad.zip \
+                 "https://www.doomworld.com/3ddownloads/ports/shareware_doom_iwad.zip"
+            unzip -d build/ build/shareware_doom_iwad.zip
+      if: ${{ always() }}
+    - name: default build using emcc
+      run: |
+            make CC=emcc -j$(nproc)
+      if: ${{ always() }}
+    - name: default build for system emulation using emcc
+      run: |
+            make distclean
+            make CC=emcc ENABLE_SYSTEM=1 -j$(nproc)
+            make distclean ENABLE_SYSTEM=1
       if: ${{ always() }}
     - name: default build with -g
       env:

mk/system.mk

@@ -12,9 +12,17 @@ $(BUILD_DTB): $(DEV_SRC)/minimal.dts
 	$(VECHO) " DTC\t$@\n"
 	$(Q)$(CC) -nostdinc -E -P -x assembler-with-cpp -undef $(CFLAGS_dt) $^ | $(DTC) - > $@
 
+# Assume the system has either GCC or Clang
+NATIVE_CC := $(shell which gcc || which clang)
+
 BIN_TO_C := $(OUT)/bin2c
 $(BIN_TO_C): tools/bin2c.c
+# emcc generates wasm but not executable, so fallback to use GCC or Clang
+ifeq ("$(CC_IS_EMCC)", "1")
+	$(Q)$(NATIVE_CC) -Wall -o $@ $^
+else
 	$(Q)$(CC) -Wall -o $@ $^
+endif
 
 BUILD_DTB2C := src/minimal_dtb.h
 $(BUILD_DTB2C): $(BIN_TO_C) $(BUILD_DTB)

mk/toolchain.mk

@@ -52,6 +52,10 @@ else ifneq ($(shell $(CC) --version | grep "Free Software Foundation"),)
      CC_IS_GCC := 1
 endif
 
+ifeq ("$(CC_IS_CLANG)$(CC_IS_GCC)$(CC_IS_EMCC)", "")
+$(error "Only supported GCC/Clang/Emcc")
+endif
+
 CFLAGS_NO_CET :=
 processor := $(shell uname -m)
 ifeq ($(processor),$(filter $(processor),i386 x86_64))