Allow -g and -O options to be specified multiple times at command line.

Author: pnkfelix

src/librustc/session/config.rs

@@ -786,8 +786,8 @@ pub fn rustc_short_optgroups() -> Vec<RustcOptGroup> {
         opt::multi("", "print", "Comma separated list of compiler information to \
                                print on stdout",
                  "[crate-name|file-names|sysroot]"),
-        opt::flag("g",  "",  "Equivalent to -C debuginfo=2"),
-        opt::flag("O", "", "Equivalent to -C opt-level=2"),
+        opt::multi("g",  "",  "Equivalent to -C debuginfo=2"),
+        opt::multi("O", "", "Equivalent to -C opt-level=2"),
         opt::opt("o", "", "Write output to <filename>", "FILENAME"),
         opt::opt("",  "out-dir", "Write output to compiler-chosen filename \
                                 in <dir>", "DIR"),