[llvm-size] Fix missing file name for darwin output format with non-Mach-O

llvm-size falls back to printing in Berkeley format, if --format=darwin is specified and a non-Mach-O object has been provided. However, it does not print the input filename when it should:

Before -
(base) xgupta@archlinux ~/llvm/llvm-project/build (main*) $ llvm-size ~/hello.o --format=darwin
   text	   data	    bss	    dec	    hex	filename
    291	      0	      0	    291	    123	%

After -
(base) xgupta@archlinux ~/llvm/llvm-project/build (main*) $ bin/llvm-size ~/hello.o --format=darwin
   text	   data	    bss	    dec	    hex	filename
    291	      0	      0	    291	    123	/home/xgupta/hello.o

Fix #42316

Reviewed By: jhenderson

Differential Revision: https://reviews.llvm.org/D132364
diff --git a/llvm/tools/llvm-size/llvm-size.cpp b/llvm/tools/llvm-size/llvm-size.cpp
index 1c7484b..d65505f 100644
--- a/llvm/tools/llvm-size/llvm-size.cpp
+++ b/llvm/tools/llvm-size/llvm-size.cpp
@@ -570,6 +570,8 @@
         else if (MachO && OutputFormat == darwin)
           outs() << a->getFileName() << "(" << o->getFileName() << "):\n";
         printObjectSectionSizes(o);
+        if (!MachO && OutputFormat == darwin)
+          outs() << o->getFileName() << " (ex " << a->getFileName() << ")\n";
         if (OutputFormat == berkeley) {
           if (MachO)
             outs() << a->getFileName() << "(" << o->getFileName() << ")\n";
@@ -836,6 +838,8 @@
     else if (MachO && OutputFormat == darwin && MoreThanOneFile)
       outs() << o->getFileName() << ":\n";
     printObjectSectionSizes(o);
+    if (!MachO && OutputFormat == darwin)
+      outs() << o->getFileName() << "\n";
     if (OutputFormat == berkeley) {
       if (!MachO || MoreThanOneFile)
         outs() << o->getFileName();