scripts/recordmcount.pl: Fix RISC-V regex for clang

Clang can generate R_RISCV_CALL_PLT relocations to _mcount:

$ llvm-objdump -dr build/riscv/init/main.o | rg mcount
                000000000000000e:  R_RISCV_CALL_PLT     _mcount
                000000000000004e:  R_RISCV_CALL_PLT     _mcount

After this, the __start_mcount_loc section is properly generated and
function tracing still works.

Link: https://github.com/ClangBuiltLinux/linux/issues/1331
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Fangrui Song <maskray@google.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

scripts/recordmcount.pl

@@ -392,7 +392,7 @@ sub check_objcopy
     $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
 } elsif ($arch eq "riscv") {
     $function_regex = "^([0-9a-fA-F]+)\\s+<([^.0-9][0-9a-zA-Z_\\.]+)>:";
-    $mcount_regex = "^\\s*([0-9a-fA-F]+):\\sR_RISCV_CALL\\s_mcount\$";
+    $mcount_regex = "^\\s*([0-9a-fA-F]+):\\sR_RISCV_CALL(_PLT)?\\s_mcount\$";
     $type = ".quad";
     $alignment = 2;
 } elsif ($arch eq "nds32") {