all: remove init interpretation during IR construction

The interp package does a much better job at interpretation, and is
implemented as a pass on the IR which makes it much easier to compose.
Also, the implementation works much better as it is based on LLVM IR
instead of Go SSA.

main_test.go

@@ -103,7 +103,6 @@ func runTest(path, tmpdir string, target string, t *testing.T) {
 		dumpSSA:    false,
 		debug:      false,
 		printSizes: "",
-		initInterp: true,
 	}
 	binary := filepath.Join(tmpdir, "test")
 	err = Build("./"+path, binary, target, config)