[cmake] Modernize some conditionals. NFC

[smeenai]

Summary

I'm not sure what the "x..." form was needed for, but it looks super
old-school and unnecessary. Just reference the variable directly and
adjust the comparison strings accordingly.

[compnerd]

Looks like a carry-over from the autoconf conversion (where it is used to deal with a posix sh limitation.

[beanz]

This is a workaround predating CMake 3.1 when they fixed the underlying issues with the expansion of variables in STREQUAL. See: https://cmake.org/cmake/help/v3.1/policy/CMP0054.html.

LGTM.

llvm/trunk/cmake/modules/LLVM-Config.cmake

 endmacro(llvm_config)
 
 
 function(explicit_llvm_config executable)
   set( link_components ${ARGN} )
 
   llvm_map_components_to_libnames(LIBRARIES ${link_components})
   get_target_property(t ${executable} TYPE)
-  if("x${t}" STREQUAL "xSTATIC_LIBRARY")
+  if(t STREQUAL "STATIC_LIBRARY")
     target_link_libraries(${executable} INTERFACE ${LIBRARIES})
-  elseif("x${t}" STREQUAL "xSHARED_LIBRARY" OR "x${t}" STREQUAL "xMODULE_LIBRARY")
+  elseif(t STREQUAL "SHARED_LIBRARY" OR t STREQUAL "MODULE_LIBRARY")
     target_link_libraries(${executable} PRIVATE ${LIBRARIES})
   else()
     # Use plain form for legacy user.
     target_link_libraries(${executable} ${LIBRARIES})
   endif()
 endfunction(explicit_llvm_config)