Add SDC (Steven's fork) as submodule and build its libdmdalloc.a

.github/workflows/main.yml

@@ -36,6 +36,30 @@ jobs:
           fi
           source ~/dlang/$HOST_DC/activate
 
+          # download & unpack prebuilt LLVM 19 for SDC
+          curl -fL -o llvm.tar.xz https://github.com/ldc-developers/llvm-project/releases/download/ldc-v19.1.3/llvm-19.1.3-linux-x86_64.tar.xz
+          mkdir llvm
+          tar -xf llvm.tar.xz --strip 1 -C llvm
+          rm llvm.tar.xz
+
+          # download & unpack prebuilt clang v15 to use as linker driver for SDC
+          # (matching the clang version used to compile the prebuilt LLVM)
+          curl -fL -o clang.tar.xz https://github.com/llvm/llvm-project/releases/download/llvmorg-15.0.6/clang+llvm-15.0.6-x86_64-linux-gnu-ubuntu-18.04.tar.xz
+          mkdir clang
+          tar -xf clang.tar.xz --strip 1 -C clang
+          rm clang.tar.xz
+          # make SDC's Makefile detect and use the ld.lld linker
+          sudo ln -sf "$PWD/clang/bin/ld.lld" /usr/bin/ld.lld
+
+          # install distro packages for SDC
+          export DEBIAN_FRONTEND=noninteractive
+          sudo apt-get -qq update
+          sudo apt-get install -qq nasm libzstd-dev
+
+          # build SDC's libdmdalloc.a
+          LLVM_CONFIG=$PWD/llvm/bin/llvm-config CC=$PWD/clang/bin/clang SDFLAGS=-O3 make -C sdc
+          ls -l sdc/lib/libdmdalloc.a
+
           # patch DMD version if this CI job was triggered by a tag
           tag=""
           if [[ '${{ github.ref }}' = refs/tags/v* ]]; then

.gitmodules

@@ -13,3 +13,7 @@
 [submodule "ninja"]
 	path = ninja
 	url = [email protected]:symmetryinvestments/ninja.git
+[submodule "sdc"]
+	path = sdc
+	url = https://github.com/schveiguy/sdc.git
+	branch = dmdbuild