[ELF] Warn about to-be-removed -d, -dc, -dp, and --[no-]define-common

See llvm#53660

Author: MaskRay

lld/ELF/Driver.cpp

@@ -1240,6 +1240,9 @@ static void readConfigs(opt::InputArgList &args) {
       error(errPrefix + toString(pat.takeError()));
   }
 
+  if (args.hasArg(OPT_define_common, OPT_no_define_common))
+    warn("-d, -dc, -dp, and --[no-]define-common will be removed. See https://github.com/llvm/llvm-project/issues/53660");
+
   cl::ResetAllOptionOccurrences();
 
   // Parse LTO options.

lld/test/ELF/relocatable-common.s

@@ -2,17 +2,19 @@
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t1.o
 # RUN: ld.lld -r %t1.o -o %t
 # RUN: llvm-readobj --symbols -r %t | FileCheck %s
-# RUN: ld.lld -r --no-define-common %t1.o -o %t
+# RUN: ld.lld -r --no-define-common %t1.o -o %t 2>&1 | FileCheck %s --check-prefix=WARN
 # RUN: llvm-readobj --symbols -r %t | FileCheck %s
-# RUN: ld.lld -r --define-common %t1.o -o %t
+# RUN: ld.lld -r --define-common %t1.o -o %t 2>&1 | FileCheck %s --check-prefix=WARN
 # RUN: llvm-readobj --symbols -r %t | FileCheck -check-prefix=DEFCOMM %s
-# RUN: ld.lld -r -d %t1.o -o %t
+# RUN: ld.lld -r -d %t1.o -o %t 2>&1 | FileCheck %s --check-prefix=WARN
 # RUN: llvm-readobj --symbols -r %t | FileCheck -check-prefix=DEFCOMM %s
-# RUN: ld.lld -r -dc %t1.o -o %t
+# RUN: ld.lld -r -dc %t1.o -o %t 2>&1 | FileCheck %s --check-prefix=WARN
 # RUN: llvm-readobj --symbols -r %t | FileCheck -check-prefix=DEFCOMM %s
-# RUN: ld.lld -r -dp %t1.o -o %t
+# RUN: ld.lld -r -dp %t1.o -o %t 2>&1 | FileCheck %s --check-prefix=WARN
 # RUN: llvm-readobj --symbols -r %t | FileCheck -check-prefix=DEFCOMM %s
 
+# WARN: warning: -d, -dc, -dp, and --[no-]define-common will be removed. See https://github.com/llvm/llvm-project/issues/53660
+
 # CHECK:        Symbol {
 # CHECK:          Name: common
 # CHECK-NEXT:     Value: 0x4