fix SymbolGraph/EmitWhileBuilding output map

the new driver fails when running this test, because the file map and
the command-line specify the same module output for both the individual
swift file and the module as a whole

Author: QuietMisdreavus

test/SymbolGraph/Inputs/EmitWhileBuilding.output.json

@@ -4,7 +4,7 @@
     },
     "EmitWhileBuilding.swift": {
         "object": "./EmitWhileBuilding.o",
-        "swiftmodule": "./EmitWhileBuilding.swiftmodule",
+        "swiftmodule": "./EmitWhileBuilding_partial.swiftmodule",
         "dependencies": "./EmitWhileBuilding.d",
         "swift-dependencies": "./EmitWhileBuilding.swiftdeps"
     }