Fix sporadic failing ghci/Linker/Dyn tests

Summary:
Multiple tests use the same source C file.
GHC was previously writing the resulting .o files
in the same folder as the source. When these tests
are run in parallel, sometimes one of the calls would
use the partial .o file and throw an error.

The .o files are moved into different folders with this
change.

Test Plan: make test -C testsuite/tests/ghci/linking/dyn

Reviewers: thomie, austin, bgamari

Reviewed By: bgamari

Differential Revision: https://phabricator.haskell.org/D1449

testsuite/tests/ghci/linking/dyn/Makefile

@@ -30,7 +30,7 @@ MY_TEST_HC_OPTS = $(filter-out -rtsopts,$(TEST_HC_OPTS)) $(CFLAGS)
 load_short_name:
 	rm -rf bin_short
 	mkdir bin_short
-	'$(TEST_HC)' $(MY_TEST_HC_OPTS) -shared A.c -o "bin_short/$(call DLL,A)"
+	'$(TEST_HC)' $(MY_TEST_HC_OPTS) -odir "bin_short" -shared A.c -o "bin_short/$(call DLL,A)"
 	rm -f bin_short/*.a
 	echo ":q" | "$(TEST_HC)" --interactive -L"./bin_short" -lA -v0
 
@@ -43,16 +43,16 @@ compile_libAS:
 compile_libAB_dep:
 	rm -rf bin_dep
 	mkdir bin_dep
-	'$(TEST_HC)' $(MY_TEST_HC_OPTS) -shared A.c -o "bin_dep/$(call DLL,A)"
-	'$(TEST_HC)' $(MY_TEST_HC_OPTS) -shared B.c -o "bin_dep/$(call DLL,B)" -lA -L"./bin_dep"
+	'$(TEST_HC)' $(MY_TEST_HC_OPTS) -odir "bin_dep" -shared A.c -o "bin_dep/$(call DLL,A)"
+	'$(TEST_HC)' $(MY_TEST_HC_OPTS) -odir "bin_dep" -shared B.c -o "bin_dep/$(call DLL,B)" -lA -L"./bin_dep"
 	rm -f bin_dep/*.a
 
 .PHONY: compile_libAB_dyn
 compile_libAB_dyn:
 	rm -rf bin_dyn
 	mkdir bin_dyn
-	'$(TEST_HC)' $(MY_TEST_HC_OPTS) -shared A.c -o "bin_dyn/$(call DLL,A)"
-	'$(TEST_HC)' $(MY_TEST_HC_OPTS) -shared B.c -o "bin_dyn/$(call DLL,B)" -lA -L"./bin_dyn"
+	'$(TEST_HC)' $(MY_TEST_HC_OPTS) -odir "bin_dyn" -shared A.c -o "bin_dyn/$(call DLL,A)"
+	'$(TEST_HC)' $(MY_TEST_HC_OPTS) -odir "bin_dyn" -shared B.c -o "bin_dyn/$(call DLL,B)" -lA -L"./bin_dyn"
 	rm -f bin_dyn/*.a
 	'$(TEST_HC)' $(TEST_HC_OPTS) -ignore-dot-ghci -v0 -o "bin_dyn/$(call EXE,T10955dyn)" -L./bin_dyn -lB -lA T10955dyn.hs -v0
 	LD_LIBRARY_PATH=./bin_dyn ./bin_dyn/$(call EXE,T10955dyn)