[cmake] Copy llvm-driver-template.cpp.in into build dir as well

We were copying it into the installed version of the directory,
but not into the one in the build directory. Because of that it
was not directly usable as a cmake module by subprojects that
also use the driver functionality.

llvm/cmake/modules/CMakeLists.txt

@@ -108,6 +108,7 @@ file(COPY .
   NO_SOURCE_PERMISSIONS
   FILES_MATCHING PATTERN *.cmake
   PATTERN CMakeFiles EXCLUDE
+  PATTERN llvm-driver-template.cpp.in
   )
 
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