build: Improvements to bundled libraries support. (#6435)

dist/installer/CMakeLists.txt

@@ -5,18 +5,24 @@ elseif(APPLE)
     set(PLATFORM "mac")
 elseif(UNIX)
     set(PLATFORM "linux")
+else()
+    message(FATAL_ERROR "Cannot build installer for this unsupported platform")
 endif()
 
 set(BUILD_DIR "${CMAKE_BINARY_DIR}/installer")
 set(DIST_DIR "${BUILD_DIR}/dist")
 set(TARGET_FILE "${DIST_DIR}/citra-setup-${PLATFORM}")
-file(MAKE_DIRECTORY ${BUILD_DIR})
 
 # Adds a custom target that will run the BuildInstaller.cmake file
 # CMake can't just run a cmake function as a custom command, so this is a way around it.
 # Calls the cmake command and runs a cmake file in "scripting" mode passing in variables with -D
 add_custom_command(OUTPUT "${TARGET_FILE}"
-    COMMAND ${CMAKE_COMMAND} -DSRC_DIR=${CMAKE_CURRENT_SOURCE_DIR} -D BUILD_DIR=${BUILD_DIR} -D TARGET_FILE=${TARGET_FILE} -P ${CMAKE_SOURCE_DIR}/CMakeModules/BuildInstaller.cmake
+    COMMAND ${CMAKE_COMMAND}
+        -DBASE_DIR=${CMAKE_SOURCE_DIR}
+        -DSRC_DIR=${CMAKE_CURRENT_SOURCE_DIR}
+        -DBUILD_DIR=${BUILD_DIR}
+        -DTARGET_FILE=${TARGET_FILE}
+        -P ${CMAKE_SOURCE_DIR}/CMakeModules/BuildInstaller.cmake
     WORKING_DIRECTORY ${BUILD_DIR}
 )