Fix CMake build when included from other project

CMakeLists.txt

@@ -27,7 +27,7 @@ if(${CMAKE_VERSION} VERSION_GREATER_EQUAL "3.15.0")
 endif()
 
 # Install custom module path
-set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_SOURCE_DIR}/cmake/")
+set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_CURRENT_SOURCE_DIR}/cmake/")
 
 include(VSForceXPToolchain) # Force XP toolchain for Visual Studio
 
@@ -52,8 +52,6 @@ set(SERVER_LIBRARY_NAME "hl" CACHE STRING "Library name for Linux/MacOS/Windows"
 # MAIN BUILD CODE \
 ###################\
 
-set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_SOURCE_DIR}/cmake/")
-
 if(CMAKE_SIZEOF_VOID_P EQUAL 8 AND NOT 64BIT)
 	if(MSVC)
 		error("UNDONE: set 32 build flags")

cmake/LibraryNaming.cmake

@@ -1,7 +1,7 @@
 include(CheckSymbolExists)
 
 # generated(see comments in public/build.h)
-set(CMAKE_REQUIRED_INCLUDES "${CMAKE_SOURCE_DIR}/public/")
+set(CMAKE_REQUIRED_INCLUDES "${PROJECT_SOURCE_DIR}/public/")
 check_symbol_exists(XASH_64BIT "build.h" XASH_64BIT)
 check_symbol_exists(XASH_AMD64 "build.h" XASH_AMD64)
 check_symbol_exists(XASH_ANDROID "build.h" XASH_ANDROID)