[sledge] Fix context name in test/Makefile

Summary:
Should have been included in:
22cbec493 [sledge] Rename contexts/profiles to be more conventional

Reviewed By: jvillard

Differential Revision: D21441538

fbshipit-source-id: 92b591171

sledge/test/Makefile

@@ -7,7 +7,7 @@
 CLANG_ARGS?=-O0
 
 # executable to test
-SLEDGE_EXE=$(CURDIR)/../_build/_install/dbg/bin/sledge
+SLEDGE_EXE=$(CURDIR)/../_build/_install/debug/bin/sledge
 
 # additional arguments to pass to sledge
 SLEDGE_ARGS?=