testdata: use the debugdir flag less often

In tiny.txt, we already check line numbers via stderr, so there's no
need to do that via -debugdir.

In syntax.txt, we only really care about what names remain in the
binary, not the names which remain in the source but don't affect the
binary.

These changes are important because -debugdir adds a non-trivial amount
of work, which will impede build caching once that feature lands. We
will likely make -debugdir support build caching eventually, but for
now, this preliminary change will make 'go test' much faster with build
caching.

And of course, the tests get simpler, which is nice.

testdata/scripts/literals.txt

@@ -49,7 +49,6 @@ grep '^\s+\w+ = append\(\w+,(\s+\w+\[\d+\][\^\-+]\w+\[\d+\],?)+\)$' .obf-src/mai
 # XorSeed obfuscator. Detect type decFunc func(byte) decFunc
 grep '^\s+type \w+ func\(byte\) \w+$' .obf-src/main/extraLiterals.go
 
-
 -- go.mod --
 module test/main
 -- main.go --

testdata/scripts/syntax.txt

@@ -1,13 +1,11 @@
 env GOPRIVATE='test/main,rsc.io/*'
 
-garble -debugdir=debug build
+garble build
 exec ./main$exe
 cmp stderr main.stderr
 
 ! binsubstr main$exe 'localName' 'globalConst' 'globalVar' 'globalType' 'valuable information' 'rsc.io'
 
-binsubstr debug/main/scopes.go 'localName' 'globalConst'
-
 [short] stop # no need to verify this with -short
 
 go build

testdata/scripts/tiny.txt

@@ -11,13 +11,7 @@ stderr '\? 0'
 
 # Default mode
 env GODEBUG=
-garble -debugdir=.obf-src build
-
-# Check for file name leak protection
-grep '^\/\/line :1$' .obf-src/main/main.go
-
-# Check for default line obfuscation
-grep '^\/\/line \w\.go:[1-9][0-9]*$' .obf-src/main/main.go
+garble build
 ! exec ./main$exe
 cmp stdout main.stdout
 stderr '\w\.go [1-9]'
@@ -47,4 +41,4 @@ func main() {
 }
 
 -- main.stdout --
-ya like jazz?
+ya like jazz?