do less work in 'go test -short'

Only reduces the approximate elapsed time on my laptop from 7.8s to
7.5s, but that's still a win.

testdata/scripts/basic.txt

@@ -1,18 +1,3 @@
-# Check that the program works as expected without garble.
-exec go build main.go
-exec ./main
-cmp stderr main.stderr
-
-# The default build includes DWARF and the symbol table.
-[!windows] [exec:readelf] exec readelf --section-headers main$exe
-[!windows] [exec:readelf] stdout 'debug_info'
-[!windows] [exec:readelf] stdout '\.symtab'
-
-# The default build includes full non-trimmed paths, as well as our names.
-# Only check $WORK on non-windows, because it's difficult to do it there.
-binsubstr main$exe 'globalVar' 'globalFunc'
-[!windows] binsubstr main$exe ${WORK@R}
-
 # Check that we fail if the user forgot -trimpath.
 ! exec go build -a -toolexec=garble main.go
 stderr 'should be used alongside -trimpath'
@@ -38,6 +23,22 @@ garble build main.go
 ! binsubstr main$exe 'globalVar'
 bincmp main$exe main_old$exe
 
+# Check that the program works as expected without garble. No need to verify
+# this when we run with -short.
+exec go build main.go
+exec ./main
+cmp stderr main.stderr
+
+# The default build includes DWARF and the symbol table.
+[!windows] [exec:readelf] exec readelf --section-headers main$exe
+[!windows] [exec:readelf] stdout 'debug_info'
+[!windows] [exec:readelf] stdout '\.symtab'
+
+# The default build includes full non-trimmed paths, as well as our names.
+# Only check $WORK on non-windows, because it's difficult to do it there.
+binsubstr main$exe 'globalVar' 'globalFunc'
+[!windows] binsubstr main$exe ${WORK@R}
+
 -- main.go --
 package main
 

testdata/scripts/modinfo.txt

@@ -1,13 +1,15 @@
-exec go build
-exec ./main
-cmp stdout main.stdout-orig
-binsubstr main$exe '(devel)'
-
 garble build
 exec ./main
 cmp stdout main.stdout
 ! binsubstr main$exe '(devel)'
 
+[short] stop # no need to verify this with -short
+
+exec go build
+exec ./main
+cmp stdout main.stdout-orig
+binsubstr main$exe '(devel)'
+
 -- go.mod --
 module foo.com/main
 -- main.go --

testdata/scripts/test.txt

@@ -1,6 +1,3 @@
-exec go test -v
-stdout 'PASS.*TestFoo'
-
 garble test -c
 binsubstr bar.test$exe 'TestFoo' 'TestSeparateFoo'
 ! binsubstr bar.test$exe 'ImportedVar'
@@ -9,6 +6,11 @@ exec ./bar.test -test.v
 stdout 'PASS.*TestFoo'
 stdout 'PASS.*TestSeparateFoo'
 
+[short] stop # no need to verify this with -short
+
+exec go test -v
+stdout 'PASS.*TestFoo'
+
 -- go.mod --
 module foo.com/bar
 -- bar.go --