Makefile.am: Don't use dots in -osuf

This fixes
  ./configure --enable-haskell-tests && make hs-tests
builds on GHC 7.8.

It changes `-osuf .ext` to `-osuf ext`; the old form was allowed in
GHC <= 7.6, but GHC 7.8 seems to have problems with it:
  https://ghc.haskell.org/trac/ghc/ticket/9760

The form without dot works in all GHC versions, and we don't have
dots in other -osuf arguments in the same file either, so this
was probably an accident.
Signed-off-by: Niklas Hambuechen <niklash@google.com>
Reviewed-by: Klaus Aehlig <aehlig@google.com>

Makefile.am

@@ -798,8 +798,8 @@ HFLAGS += -DTEST
 endif
 
 HTEST_FLAGS = $(HFLAGS) -fhpc -itest/hs \
-	-osuf .$(HTEST_SUFFIX)_o \
-	-hisuf .$(HTEST_SUFFIX)_hi
+	-osuf $(HTEST_SUFFIX)_o \
+	-hisuf $(HTEST_SUFFIX)_hi
 if !HPROFILE
 HTEST_FLAGS += $(HFLAGS_NOPROF)
 endif