win32: use jwasm as masm-compatible assembler on MinGW

Author: illwieckz

CMakeLists.txt

@@ -2,7 +2,11 @@ cmake_minimum_required(VERSION 3.28)
 
 project(native_client C CXX ASM)
 
-if (WIN32 AND NOT MINGW)
+if (WIN32)
+	if (NOT MSVC AND NOT CMAKE_ASM_MASM_COMPILER)
+		set(CMAKE_ASM_MASM_COMPILER "jwasm")
+	endif()
+
 	enable_language(ASM_MASM)
 endif()
 
@@ -11,6 +15,14 @@ list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake")
 include(DaemonPlatform/Platform)
 include(NaClFlags)
 
+if (WIN32 AND NOT MSVC)
+	if (ARCH STREQUAL "i686")
+		list(APPEND CMAKE_ASM_MASM_FLAGS "-coff")
+	elseif(ARCH STREQUAL "amd64")
+		list(APPEND CMAKE_ASM_MASM_FLAGS "-win64")
+	endif()
+endif()
+
 if (NOT PYTHON)
 	set(PYTHON "python3")
 endif()

src/trusted/service_runtime/CMakeLists.txt

@@ -103,12 +103,8 @@ elseif (ARCH STREQUAL "amd64")
 			# This use of win64_asm_env causes an invocation of MSVC, even if sel_ldr
 			# would not otherwise be actually built. So don't include it if we aren't
 			# actually building sel_ldr
-			if (MSVC)
-				add_library(nacl_switch_unwind_win OBJECT "arch/x86_64/nacl_switch_unwind_win.asm")
-				list(APPEND LDR_LIBS nacl_switch_unwind_win)
-			else()
-				message(WARNING "Cannot build nacl_switch_unwind_win without MSVC ml")
-			endif()
+			add_library(nacl_switch_unwind_win OBJECT "arch/x86_64/nacl_switch_unwind_win.asm")
+			list(APPEND LDR_LIBS nacl_switch_unwind_win)
 		endif()
 	else()
 		list(APPEND LDR_INPUTS "arch/x86_64/sel_addrspace_posix_x86_64.c")