perl: fix configure phase for Aarch32

In "perl: fuse configureFlags" [1] the effects of the preConfigure
phase were merged into configureFlags. After this change values with
spaces do not reach the configure script intact.

The only flag this affects is `ldflags` for Aarch32 and Mips, and perl
builds without it on armv7l-linux so it's probably no longer required
on any platform.

Fixes:

    configuring
    configure flags: -de -Dcc=cc <...> -Dldflags=\"-lm -lrt\"
    ./Configure: eval: line 1677: unexpected EOF while looking for matching `"'
    ./Configure: eval: line 1678: syntax error: unexpected end of file
    Configure: unknown option -lrt"

[1] 3b50d0462a

pkgs/development/interpreters/perl/default.nix

@@ -96,8 +96,7 @@ let
         "-Dprefix=${placeholder "out"}"
         "-Dman1dir=${placeholder "out"}/share/man/man1"
         "-Dman3dir=${placeholder "out"}/share/man/man3"
-      ]
-      ++ optional (stdenv.isAarch32 || stdenv.isMips) "-Dldflags=\"-lm -lrt\"";
+      ];
 
     configureScript = optionalString (!crossCompiling) "${stdenv.shell} ./Configure";