[clang][driver] Fix float128 diagnostics with glibc >= 2.32

Fix checking for an unsupported stdlib++.

Differential Revision: https://reviews.llvm.org/D121209

(cherry picked from commit 5b7941a)

Author: tbaederr

clang/lib/Driver/ToolChains/PPCLinux.cpp

@@ -76,9 +76,11 @@ bool PPCLinuxToolChain::SupportIEEEFloat128(
   if (Args.hasArg(options::OPT_nostdlib, options::OPT_nostdlibxx))
     return true;
 
+  CXXStdlibType StdLib = ToolChain::GetCXXStdlibType(Args);
   bool HasUnsupportedCXXLib =
-      ToolChain::GetCXXStdlibType(Args) == CST_Libcxx &&
-      GCCInstallation.getVersion().isOlderThan(12, 1, 0);
+      StdLib == CST_Libcxx ||
+      (StdLib == CST_Libstdcxx &&
+       GCCInstallation.getVersion().isOlderThan(12, 1, 0));
 
   return GlibcSupportsFloat128(Linux::getDynamicLinker(Args)) &&
          !(D.CCCIsCXX() && HasUnsupportedCXXLib);