Unable to parse source maps

[sgammon]

When building SCSS before running it through GSS, if the SCSS is configured to output source maps, I get the following error from GSS:

Compiler parsing error: Parse error in bazel-out/darwin-fastbuild/bin/bloombox/ui/style/terms.css.map at line 1 column 1:
{"version":3,"sourceRoot":"","sources":["<lots-of-paths>"],"names":[],"mappings":"AACA;AAAA;AAAA;AAGA;EACE;EACA;EACA;EACA;;AAGF;EACE;EACA;EACA;EACA;EACA;EACA;EACA;EACA;EACA;EACA;EACA;EACA;EACA;;;ACxBF;AAAA;AAAA;AAAA;AAAA;AAAA;AAAA;AAAA;AAAA;AAAA;AAAA;AAAA;AAAA;AAAA;AAAA;AAgBA;AAikBA;AC7kBA;EACE;EACA;EACA;EACA;EACA;EACA,aCgBe;;;ADbjB;EACE;;;AAGF;EACE;;;AAGF;EACE;;;AAGF;EACE;EACA;EACA;EACA;EACA;EACA;EACA;EACA;;;AAGF;EACE;;;AAGF;EACE;;AAEA;EACE;;;AEzCJ;EACE","file":"some-file.css"}
^

com.google.common.css.compiler.ast.GssParserException: Parse error in bazel-out/darwin-fastbuild/bin/bloombox/ui/style/terms.css.map at line 1 column 1:
{"version":3,"sourceRoot":"","sources":["<lots-of-paths>"],"names":[],"mappings":"AACA;AAAA;AAAA;AAGA;EACE;EACA;EACA;EACA;;AAGF;EACE;EACA;EACA;EACA;EACA;EACA;EACA;EACA;EACA;EACA;EACA;EACA;EACA;;;ACxBF;AAAA;AAAA;AAAA;AAAA;AAAA;AAAA;AAAA;AAAA;AAAA;AAAA;AAAA;AAAA;AAAA;AAAA;AAgBA;AAikBA;AC7kBA;EACE;EACA;EACA;EACA;EACA;EACA,aCgBe;;;ADbjB;EACE;;;AAGF;EACE;;;AAGF;EACE;;;AAGF;EACE;EACA;EACA;EACA;EACA;EACA;EACA;EACA;;;AAGF;EACE;;;AAGF;EACE;;AAEA;EACE;;;AEzCJ;EACE","file":"some-file.css"}
^

	at com.google.common.css.compiler.ast.GssParserCC.parse(GssParserCC.java:214)
	at com.google.common.css.compiler.ast.GssParserCC.parse(GssParserCC.java:234)
	at com.google.common.css.compiler.ast.AbstractGssParser.parseInternal(AbstractGssParser.java:56)
	at com.google.common.css.compiler.ast.GssParser.parse(GssParser.java:46)
	at com.google.common.css.compiler.ast.GssParser.parse(GssParser.java:42)
	at com.google.common.css.compiler.commandline.DefaultCommandLineCompiler.parseAndPrint(DefaultCommandLineCompiler.java:126)
	at com.google.common.css.compiler.commandline.DefaultCommandLineCompiler.compile(DefaultCommandLineCompiler.java:110)
	at com.google.common.css.compiler.commandline.DefaultCommandLineCompiler.execute(DefaultCommandLineCompiler.java:156)
	at com.google.common.css.compiler.commandline.ClosureCommandLineCompiler.executeJob(ClosureCommandLineCompiler.java:385)
	at com.google.common.css.compiler.commandline.ClosureCommandLineCompiler.main(ClosureCommandLineCompiler.java:451)
Caused by: com.google.common.css.compiler.ast.ParseException: Encountered " "{" "{ "" at line 1, column 1.
Was expecting one of:
    <EOF> 
    ":" ...
    "." ...
    "*" ...
    "[" ...
    "<!--" ...
    "-->" ...
    <S> ...
    <HASH_NAME> ...
    <IDENTIFIER> ...
    <ATLIST> ...
    <WEBKITKEYFRAMES> ...
    <ATRULESWITHDECLBLOCK> ...
    <ATKEYWORD> ...
    
	at com.google.common.css.compiler.ast.GssParserCC.generateParseException(GssParserCC.java:5284)
	at com.google.common.css.compiler.ast.GssParserCC.jj_consume_token(GssParserCC.java:5149)
	at com.google.common.css.compiler.ast.GssParserCC.start(GssParserCC.java:3931)
	at com.google.common.css.compiler.ast.GssParserCC.parse(GssParserCC.java:209)
	... 9 more

#61, which was fixed by @iflan, doesn't mention whether incoming source maps are supported.