public long getStartIndex() {
		return _machHeaderStartIndex;
	}
Returns the start index that should be used for calculating offsets.
This will be 0 for things such as the dyld shared cache where offsets are
based off the beginning of the file.

@return the start index that should be used for calculating offsets
Ghidra/Features/Base/src/main/java/ghidra/app/util/bin/format/macho/MachHeader.java