Add test mode for string-based memory initializer

Author: gagern

tests/test_core.py

@@ -7387,6 +7387,7 @@ def setUp(self):
 asm2g = make_run("asm2g", compiler=CLANG, emcc_args=["-O2", "-g", "-s", "ASSERTIONS=1", "-s", "SAFE_HEAP=1"])
 asm1i = make_run("asm1i", compiler=CLANG, emcc_args=["-O1", '-s', 'EMTERPRETIFY=1'])
 asm3i = make_run("asm3i", compiler=CLANG, emcc_args=["-O3", '-s', 'EMTERPRETIFY=1'])
+asm2m = make_run("asm2m", compiler=CLANG, emcc_args=["-O2", "--memory-init-file", "0", "-s", "MEM_INIT_METHOD=2"])
 
 # Legacy test modes - 
 asm2nn = make_run("asm2nn", compiler=CLANG, emcc_args=["-O2"], env={"EMCC_NATIVE_OPTIMIZER": "0"})