Merge branch 'cmake_nasm' into 'master'

CMake: Fix nasm Linux builds

When compiling under Linux with CMake and nasm/yasm enabled, the operation would fail during linking with undefined symbols related to the tmap files.
This commit adds support for passing flags to the assembler and passes ```-DLINUX``` in order to compile.

After this change, binaries are successfully compiled with either nasm or yasm on Linux systems.
Tested on Ubuntu.

See merge request !153

src/CMakeLists.txt

@@ -390,11 +390,18 @@ if(${SRB2_CONFIG_HWRENDER} AND ${SRB2_CONFIG_STATIC_OPENGL})
 endif()
 
 if(${SRB2_CONFIG_USEASM})
+	#SRB2_ASM_FLAGS can be used to pass flags to either nasm or yasm.
+	if(${CMAKE_SYSTEM} MATCHES "Linux")
+		set(SRB2_ASM_FLAGS "-DLINUX ${SRB2_ASM_FLAGS}")
+	endif()
+
 	if(${SRB2_CONFIG_YASM})
 		set(CMAKE_ASM_YASM_SOURCE_FILE_EXTENSIONS ${CMAKE_ASM_YASM_SOURCE_FILE_EXTENSIONS} nas)
+		set(CMAKE_ASM_YASM_FLAGS "${SRB2_ASM_FLAGS}" CACHE STRING "Flags used by the assembler during all build types.")
 		enable_language(ASM_YASM)
 	else()
 		set(CMAKE_ASM_NASM_SOURCE_FILE_EXTENSIONS ${CMAKE_ASM_NASM_SOURCE_FILE_EXTENSIONS} nas)
+		set(CMAKE_ASM_NASM_FLAGS "${SRB2_ASM_FLAGS}" CACHE STRING "Flags used by the assembler during all build types.")
 		enable_language(ASM_NASM)
 	endif()
 	set(SRB2_USEASM ON)