Fix #2197 (properly this time)

$ ./inplace/bin/ghc-stage2 --interactive
GHCi, version 6.11.20090701: http://www.haskell.org/ghc/  :? for help
ghc-stage2: GHCi cannot be used when compiled with -prof
[1]    32473 exit 1     ./inplace/bin/ghc-stage2 --interactive

1 files changed, 10 insertions, 0 deletions

diff --git a/rts/RtsUtils.c b/rts/RtsUtils.c
index dda9660b14..3091aa1f89 100644
--- a/rts/RtsUtils.c
+++ b/rts/RtsUtils.c
@@ -465,3 +465,13 @@ void printRtsInfo(void) {
     printf(" ]\n");
 }
 
+// Provides a way for Haskell programs to tell whether they're being
+// profiled or not.  GHCi uses it (see #2197).
+int rts_isProfiled(void)
+{
+#ifdef PROFILING
+    return 1;
+#else
+    return 0;
+#endif
+}