compiler: add support for reading embedcfg files

This is the code that parses an embedcfg file, which is a JSON file
created by the go command when it sees go:embed directives.  This code
is not yet called, and does not yet do anything.  It's being sent as a
separate CL to isolate just the JSON parsing code.

Change-Id: I3b13e7434eecc6367bb465e4c29491801bdd24d1
Trust: Ian Lance Taylor <>
Reviewed-by: Than McIntosh <>
2 files changed