Tidy up `pragma comment lib` handling and testing

A bit of historical research shows that over the years:
Commit 99efc036 added `pragma comment lib` support for PS4.
Commit fd4db533 added `pragma comment lib` support for all ELF targets.
Commit 1d16515f reworked dependent-library support for all ELF targets.

The upshot is that some PS4-specific code became dead, and the
testing became somewhat fragmented.  I've removed the dead code and
combined the previous PS4-specific and linux-specific tests for the
diagnostics into one generic ELF test.
Also added a couple of PS5 runs while I was in there.

clang/lib/Parse/ParsePragma.cpp

@@ -3027,14 +3027,6 @@ void PragmaCommentHandler::HandlePragma(Preprocessor &PP,
     return;
   }
 
-  // On PS4, issue a warning about any pragma comments other than
-  // #pragma comment lib.
-  if (PP.getTargetInfo().getTriple().isPS4() && Kind != PCK_Lib) {
-    PP.Diag(Tok.getLocation(), diag::warn_pragma_comment_ignored)
-      << II->getName();
-    return;
-  }
-
   // Read the optional string if present.
   PP.Lex(Tok);
   std::string ArgumentString;

clang/test/CodeGen/pragma-comment.c

@@ -4,6 +4,7 @@
 // RUN: %clang_cc1 %s -triple thumbv7-linux-gnueabihf -fms-extensions -emit-llvm -o - | FileCheck -check-prefix ELF %s --implicit-check-not llvm.linker.options
 // RUN: %clang_cc1 %s -triple i686-pc-linux -fms-extensions -emit-llvm -o - | FileCheck -check-prefix ELF %s --implicit-check-not llvm.linker.options
 // RUN: %clang_cc1 %s -triple x86_64-scei-ps4 -fms-extensions -emit-llvm -o - | FileCheck -check-prefix ELF %s --implicit-check-not llvm.linker.options
+// RUN: %clang_cc1 %s -triple x86_64-sie-ps5 -fms-extensions -emit-llvm -o - | FileCheck -check-prefix ELF %s --implicit-check-not llvm.linker.options
 // RUN: %clang_cc1 %s -triple aarch64-windows-msvc -fms-extensions -emit-llvm -o - | FileCheck %s
 
 #pragma comment(lib, "msvcrt.lib")

clang/test/Preprocessor/pragma-comment-elf.c

@@ -1,6 +1,8 @@
-// RUN: %clang_cc1 %s -triple x86_64-scei-ps4 -fsyntax-only -verify -fms-extensions 
+// RUN: %clang_cc1 %s -fsyntax-only -verify -fms-extensions -triple x86_64-scei-ps4
+// RUN: %clang_cc1 %s -fsyntax-only -verify -fms-extensions -triple x86_64-sie-ps5
+// RUN: %clang_cc1 %s -fsyntax-only -verify -fms-extensions -triple i686-unknown-linux-gnu
 
-// On PS4, issue a diagnostic that pragma comments are ignored except:
+// On ELF targets, issue a diagnostic that pragma comments are ignored except:
 //   #pragma comment lib
 
 #pragma comment(lib)

clang/test/Preprocessor/pragma-comment-linux.c

@@ -1,5 +0,0 @@
-// RUN: %clang_cc1 -triple i686-unknown-linux-gnu -fsyntax-only -verify %s -Wunknown-pragmas
-
-#pragma comment(linker, "")
-// expected-warning@-1 {{'#pragma comment linker' ignored}}
-