Fix ASAN CRT: don't pass any CRT flag when ASAN is enabled

clang-cl with -fsanitize=address rejects ALL explicit CRT flags
(/MT, /MTd, /MD, /MDd). Let clang-cl manage its own CRT selection
for ASAN builds.

Author: Jarred-Sumner

windows-release.ps1

@@ -71,12 +71,10 @@ $env:PATH = $PathWithPerl
 $env:CFLAGS = "/Zi"
 $env:CXXFLAGS = "/Zi"
 
-# ASAN requires the dynamic CRT (/MD or /MDd) - static CRT (/MT, /MTd) is incompatible
+# ASAN with clang-cl manages its own CRT selection — passing any explicit CRT
+# flag (/MT, /MTd, /MD, /MDd) causes "invalid argument not allowed with -fsanitize=address"
 if ($ENABLE_SANITIZERS) {
-    $CmakeMsvcRuntimeLibrary = "MultiThreadedDLL"
-    if ($CMAKE_BUILD_TYPE -eq "Debug") {
-        $CmakeMsvcRuntimeLibrary = "MultiThreadedDebugDLL"
-    }
+    $CmakeMsvcRuntimeLibrary = ""
 } else {
     $CmakeMsvcRuntimeLibrary = "MultiThreaded"
     if ($CMAKE_BUILD_TYPE -eq "Debug") {
@@ -126,39 +124,51 @@ if ($ENABLE_SANITIZERS -and $ClangLibPath) {
     }
 }
 
-cmake -S . -B $WebKitBuild `
-    -DPORT="JSCOnly" `
-    -DENABLE_STATIC_JSC=ON `
-    -DALLOW_LINE_AND_COLUMN_NUMBER_IN_BUILTINS=ON `
-    "-DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}" `
-    -DUSE_THIN_ARCHIVES=OFF `
-    -DENABLE_JIT=ON `
-    -DENABLE_DFG_JIT=ON `
-    -DENABLE_FTL_JIT=ON `
-    -DENABLE_WEBASSEMBLY_BBQJIT=ON `
-    -DENABLE_WEBASSEMBLY_OMGJIT=ON `
-    -DENABLE_SAMPLING_PROFILER=ON `
-    "-DENABLE_WEBASSEMBLY=${WebAssemblyState}" `
-    -DUSE_BUN_JSC_ADDITIONS=ON `
-    -DUSE_BUN_EVENT_LOOP=ON `
-    -DENABLE_BUN_SKIP_FAILING_ASSERTIONS=ON `
-    "-DICU_ROOT=${ICU_STATIC_ROOT}" `
-    "-DICU_LIBRARY=${ICU_STATIC_LIBRARY}" `
-    "-DICU_INCLUDE_DIR=${ICU_STATIC_INCLUDE_DIR}" `
-    "-DCMAKE_C_COMPILER=${ClangPath}" `
-    "-DCMAKE_CXX_COMPILER=${ClangPath}" `
-    "-DCMAKE_LINKER=${LldLinkPath}" `
-    "-DCMAKE_C_FLAGS_RELEASE=/Zi /O2 /Ob2 /DNDEBUG /DU_STATIC_IMPLEMENTATION ${ARM64SehWorkaround}" `
-    "-DCMAKE_CXX_FLAGS_RELEASE=/Zi /O2 /Ob2 /DNDEBUG /DU_STATIC_IMPLEMENTATION /clang:-fno-c++-static-destructors ${ARM64SehWorkaround}" `
-    "-DCMAKE_C_FLAGS_DEBUG=/Zi /FS /O0 /Ob0 /DU_STATIC_IMPLEMENTATION ${ARM64SehWorkaround}" `
-    "-DCMAKE_CXX_FLAGS_DEBUG=/Zi /FS /O0 /Ob0 /DU_STATIC_IMPLEMENTATION /clang:-fno-c++-static-destructors ${ARM64SehWorkaround}" `
-    -DENABLE_REMOTE_INSPECTOR=ON `
-    "-DCMAKE_MSVC_RUNTIME_LIBRARY=${CmakeMsvcRuntimeLibrary}" `
-    "-DENABLE_SANITIZERS=${ENABLE_SANITIZERS}" `
-    "-DENABLE_ASSERTS=${ENABLE_ASSERTS}" `
-    "-DCLANG_LIB_PATH=${ClangRtLibPath}" `
-    -G Ninja
-# TODO: "-DCMAKE_MSVC_RUNTIME_LIBRARY=MultiThreaded" `
+$cmakeArgs = @(
+    "-S", ".",
+    "-B", $WebKitBuild,
+    "-DPORT=JSCOnly",
+    "-DENABLE_STATIC_JSC=ON",
+    "-DALLOW_LINE_AND_COLUMN_NUMBER_IN_BUILTINS=ON",
+    "-DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}",
+    "-DUSE_THIN_ARCHIVES=OFF",
+    "-DENABLE_JIT=ON",
+    "-DENABLE_DFG_JIT=ON",
+    "-DENABLE_FTL_JIT=ON",
+    "-DENABLE_WEBASSEMBLY_BBQJIT=ON",
+    "-DENABLE_WEBASSEMBLY_OMGJIT=ON",
+    "-DENABLE_SAMPLING_PROFILER=ON",
+    "-DENABLE_WEBASSEMBLY=${WebAssemblyState}",
+    "-DUSE_BUN_JSC_ADDITIONS=ON",
+    "-DUSE_BUN_EVENT_LOOP=ON",
+    "-DENABLE_BUN_SKIP_FAILING_ASSERTIONS=ON",
+    "-DICU_ROOT=${ICU_STATIC_ROOT}",
+    "-DICU_LIBRARY=${ICU_STATIC_LIBRARY}",
+    "-DICU_INCLUDE_DIR=${ICU_STATIC_INCLUDE_DIR}",
+    "-DCMAKE_C_COMPILER=${ClangPath}",
+    "-DCMAKE_CXX_COMPILER=${ClangPath}",
+    "-DCMAKE_LINKER=${LldLinkPath}",
+    "-DCMAKE_C_FLAGS_RELEASE=/Zi /O2 /Ob2 /DNDEBUG /DU_STATIC_IMPLEMENTATION ${ARM64SehWorkaround}",
+    "-DCMAKE_CXX_FLAGS_RELEASE=/Zi /O2 /Ob2 /DNDEBUG /DU_STATIC_IMPLEMENTATION /clang:-fno-c++-static-destructors ${ARM64SehWorkaround}",
+    "-DCMAKE_C_FLAGS_DEBUG=/Zi /FS /O0 /Ob0 /DU_STATIC_IMPLEMENTATION ${ARM64SehWorkaround}",
+    "-DCMAKE_CXX_FLAGS_DEBUG=/Zi /FS /O0 /Ob0 /DU_STATIC_IMPLEMENTATION /clang:-fno-c++-static-destructors ${ARM64SehWorkaround}",
+    "-DENABLE_REMOTE_INSPECTOR=ON",
+    "-DENABLE_SANITIZERS=${ENABLE_SANITIZERS}",
+    "-DENABLE_ASSERTS=${ENABLE_ASSERTS}",
+    "-DCLANG_LIB_PATH=${ClangRtLibPath}",
+    "-G", "Ninja"
+)
+
+# ASAN with clang-cl manages its own CRT — any explicit CRT flag (/MT, /MTd, /MD, /MDd) causes errors.
+# Set to empty to prevent CMake from adding any CRT flag; clang-cl will select the right CRT.
+if ($ENABLE_SANITIZERS) {
+    $cmakeArgs += "-DCMAKE_MSVC_RUNTIME_LIBRARY="
+    $cmakeArgs += "-DCMAKE_POLICY_CMP0091=NEW"
+} else {
+    $cmakeArgs += "-DCMAKE_MSVC_RUNTIME_LIBRARY=${CmakeMsvcRuntimeLibrary}"
+}
+
+cmake @cmakeArgs
 if ($LASTEXITCODE -ne 0) { throw "cmake failed with exit code $LASTEXITCODE" }
 
 # Workaround for what is probably a CMake bug