Implemented linking to a dummy ASan runtime

tests_lit/asan_tests/startinitcall.ll

+; Test for a call to __asan_init in _start
+
+; REQUIRES: allow_dump
+
+; RUN: %p2i -i %s --args -verbose=inst -threads=0 -fsanitize-address \
+; RUN:     | FileCheck --check-prefix=DUMP %s
+
+; notStart() should not be instrumented
+define internal void @notStart() {
+  ret void
+}
+
+; DUMP-LABEL: ================ Instrumented CFG ================
+; DUMP-NEXT: define internal void @notStart(
+; DUMP-NEXT: __0:
+; DUMP-NOT: __asan_init()
+; DUMP: }
+
+; _start() should be instrumented
+define void @_start() {
+  ret void
+}
+
+; DUMP-LABEL: ================ Instrumented CFG ================
+; DUMP-NEXT: define void @_start(
+; DUMP-NEXT: __0:
+; DUMP-NEXT: call void @__asan_init()