CMake: Do not set CMAKE_AR

The variable for archiver is automatically set by CMake. There is
no need to explicitly set it, unless a project really needs to
override the default archiver.

Author: LDong-Arm

tools/cmake/toolchains/ARM.cmake

@@ -4,7 +4,6 @@
 set(CMAKE_ASM_COMPILER "armclang")
 set(CMAKE_C_COMPILER "armclang")
 set(CMAKE_CXX_COMPILER "armclang")
-set(CMAKE_AR "armar")
 set(ARM_ELF2BIN "fromelf")
 set_property(GLOBAL PROPERTY ELF2BIN ${ARM_ELF2BIN})