cmd/go: make assertions more precise in TestScript/gcflags_patterns

This fixes a rare test flake observed in
https://build.golang.org/log/18e531785e7f8b3e6a6d5231787a9d8bdd4a60ea.

Change-Id: I0986752f5c1abc626070b9f8ecf34c629a15cd2a
Reviewed-on: https://go-review.googlesource.com/c/go/+/359735
Trust: Bryan C. Mills <[email protected]>
Run-TryBot: Bryan C. Mills <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>

Author: Bryan C. Mills

src/cmd/go/testdata/script/gcflags_patterns.txt

@@ -7,24 +7,24 @@ env GOCACHE=$WORK/gocache  # Looking for compile commands, so need a clean cache
 
 # -gcflags=-e applies to named packages, not dependencies
 go build -n -v -gcflags=-e z1 z2
-stderr 'compile.* -p z1.* -e'
-stderr 'compile.* -p z2.* -e'
+stderr 'compile.* -p z1.* -e '
+stderr 'compile.* -p z2.* -e '
 stderr 'compile.* -p y'
-! stderr 'compile.* -p [^z].* -e'
+! stderr 'compile.* -p [^z].* -e '
 
 # -gcflags can specify package=flags, and can be repeated; last match wins
 go build -n -v -gcflags=-e -gcflags=z1=-N z1 z2
-stderr 'compile.* -p z1.* -N'
-! stderr 'compile.* -p z1.* -e'
-! stderr 'compile.* -p z2.* -N'
-stderr 'compile.* -p z2.* -e'
+stderr 'compile.* -p z1.* -N '
+! stderr 'compile.* -p z1.* -e '
+! stderr 'compile.* -p z2.* -N '
+stderr 'compile.* -p z2.* -e '
 stderr 'compile.* -p y'
-! stderr 'compile.* -p [^z].* -e'
-! stderr 'compile.* -p [^z].* -N'
+! stderr 'compile.* -p [^z].* -e '
+! stderr 'compile.* -p [^z].* -N '
 
 # -gcflags can have arbitrary spaces around the flags
 go build -n -v -gcflags='  z1 =  	-e 	' z1
-stderr 'compile.* -p z1.* -e'
+stderr 'compile.* -p z1.* -e '
 
 # -gcflags='all=-e' should apply to all packages, even with go test
 go test -c -n -gcflags='all=-e' z1