remove unnecessary variable expansion

Author: nickdesaulniers

libc/cmake/modules/LLVMLibCCheckCpuFeatures.cmake

@@ -5,10 +5,10 @@
 # Initialize ALL_CPU_FEATURES as empty list.
 set(ALL_CPU_FEATURES "")
 
-if(${LIBC_TARGET_ARCHITECTURE_IS_X86_64})
+if(LIBC_TARGET_ARCHITECTURE_IS_X86_64)
   set(ALL_CPU_FEATURES SSE2 SSE4_2 AVX AVX2 AVX512F AVX512BW FMA)
   set(LIBC_COMPILE_OPTIONS_NATIVE -march=native)
-elseif(${LIBC_TARGET_ARCHITECTURE_IS_AARCH64})
+elseif(LIBC_TARGET_ARCHITECTURE_IS_AARCH64)
   set(ALL_CPU_FEATURES "FullFP16")
   set(LIBC_COMPILE_OPTIONS_NATIVE -mcpu=native)
 endif()