build: spell the linker suffix properly on Windows

Windows requires that the .exe suffix be present to use the tools from
the Android NDK.

Author: compnerd

src/CMakeLists.txt

@@ -116,9 +116,17 @@ if(ENABLE_SWIFT)
                           POSITION_INDEPENDENT_CODE YES)
 
   if(USE_LLD_LINKER)
-    set(use_ld_flag -use-ld=lld)
+    if(CMAKE_HOST_SYSTEM_NAME STREQUAL Windows)
+      set(use_ld_flag -use-ld=lld.exe)
+    else()
+      set(use_ld_flag -use-ld=lld)
+    endif()
   elseif(USE_GOLD_LINKER)
-    set(use_ld_flag -use-ld=gold)
+    if(CMAKE_HOST_SYSTEM_NAME STREQUAL Windows)
+      set(use_ld_flag -use-ld=gold.exe)
+    else()
+      set(use_ld_flag -use-ld=gold)
+    endif()
   endif()
 
   add_swift_library(swiftDispatch