Add a test for trac #1322 (ghc --make recompiles hs-boot files unnecessarily)

testsuite/tests/ghc-regress/driver/recomp002/Makefile

+TOP=../../../..
+include $(TOP)/mk/boilerplate.mk
+include $(TOP)/mk/test.mk
+
+# Recompilation tests
+
+clean:
+	@rm -f *.o*
+	@rm -f *.hi*
+
+# Only the first invocation should print any "Compiling" messages
+
+recomp002: clean
+	@$(TEST_HC) --make Q.hs
+	@echo Middle >&2
+	@$(TEST_HC) --make Q.hs

testsuite/tests/ghc-regress/driver/recomp002/Q.hs

+
+module Q where
+
+import {-# SOURCE #-} W
+

testsuite/tests/ghc-regress/driver/recomp002/W.hs

+
+module W where
+
+import Q
+

testsuite/tests/ghc-regress/driver/recomp002/W.hs-boot

+
+module W where
+

testsuite/tests/ghc-regress/driver/recomp002/all.T

+test('recomp002', skip_if_fast, run_command, ['$MAKE -s --no-print-directory recomp002'])
+
+if default_testopts.cleanup != '':
+    runCmd('$MAKE -C ' + in_testdir('') + ' clean')

testsuite/tests/ghc-regress/driver/recomp002/recomp002.stderr

+[1 of 3] Compiling W[boot]          ( W.hs-boot, W.o-boot )
+[2 of 3] Compiling Q                ( Q.hs, Q.o )
+[3 of 3] Compiling W                ( W.hs, W.o )
+Middle