ASM: Detect compiler id for Clang used as Assembler

Add missing vendor table entries for Clang and AppleClang to identify
them.  Previously this worked only if Clang was also enabled as a C or
CXX compiler first because we used to copy the C compiler id.  However,
that was removed by commit v3.13.0-rc1~44^2 (ASM: Search for full path
even when using C or C++ compiler, 2018-09-26).

Fixes: #18575

Modules/CMakeDetermineASMCompiler.cmake

@@ -58,6 +58,14 @@ if(NOT CMAKE_ASM${ASM_DIALECT}_COMPILER_ID)
   set(CMAKE_ASM${ASM_DIALECT}_COMPILER_ID_VENDOR_FLAGS_GNU "--version")
   set(CMAKE_ASM${ASM_DIALECT}_COMPILER_ID_VENDOR_REGEX_GNU "(GNU assembler)|(GCC)|(Free Software Foundation)")
 
+  list(APPEND CMAKE_ASM${ASM_DIALECT}_COMPILER_ID_VENDORS Clang )
+  set(CMAKE_ASM${ASM_DIALECT}_COMPILER_ID_VENDOR_FLAGS_Clang "--version")
+  set(CMAKE_ASM${ASM_DIALECT}_COMPILER_ID_VENDOR_REGEX_Clang "(clang version)")
+
+  list(APPEND CMAKE_ASM${ASM_DIALECT}_COMPILER_ID_VENDORS AppleClang )
+  set(CMAKE_ASM${ASM_DIALECT}_COMPILER_ID_VENDOR_FLAGS_AppleClang "--version")
+  set(CMAKE_ASM${ASM_DIALECT}_COMPILER_ID_VENDOR_REGEX_AppleClang "(Apple LLVM version)")
+
   list(APPEND CMAKE_ASM${ASM_DIALECT}_COMPILER_ID_VENDORS HP )
   set(CMAKE_ASM${ASM_DIALECT}_COMPILER_ID_VENDOR_FLAGS_HP "-V")
   set(CMAKE_ASM${ASM_DIALECT}_COMPILER_ID_VENDOR_REGEX_HP "HP C")