build: account for spaces in the toolchain (#1030)

If the macro library path contains a space, the invocation will
improperly truncate it. Account for this eventuality.

Author: compnerd

Sources/CMakeLists.txt

@@ -94,10 +94,10 @@ if(NOT SwiftTesting_MACRO_PATH)
 elseif(SwiftTesting_MACRO_PATH)
   if(SwiftTesting_MACRO_PATH MATCHES [[\.(dylib|so|dll)$]])
     message(STATUS "TestingMacros: ${SwiftTesting_MACRO_PATH} (shared library)")
-    add_compile_options("$<$<COMPILE_LANGUAGE:Swift>:SHELL:-load-plugin-library ${SwiftTesting_MACRO_PATH}>")
+    add_compile_options("$<$<COMPILE_LANGUAGE:Swift>:SHELL:-load-plugin-library \"${SwiftTesting_MACRO_PATH}\">")
   else()
     message(STATUS "TestingMacros: ${SwiftTesting_MACRO_PATH} (executable)")
-    add_compile_options("$<$<COMPILE_LANGUAGE:Swift>:SHELL:-load-plugin-executable ${SwiftTesting_MACRO_PATH}#TestingMacros>")
+    add_compile_options("$<$<COMPILE_LANGUAGE:Swift>:SHELL:-load-plugin-executable \"${SwiftTesting_MACRO_PATH}#TestingMacros\">")
   endif()
 endif()