cmd/go: relax the regular expression of TestScript/list_pkgconfig_error

Fixes #68283

Change-Id: Ia6af550f0fc232e4ae6f7ea96370138e958aaca2
GitHub-Last-Rev: 206ce8b
GitHub-Pull-Request: #68324
Reviewed-on: https://go-review.googlesource.com/c/go/+/596935
Reviewed-by: David Chase <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Auto-Submit: Ian Lance Taylor <[email protected]>
Reviewed-by: Michael Matloob <[email protected]>

Author: qiulaidongfeng

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

@@ -2,7 +2,9 @@
 [!exec:pkg-config] skip 'test requires pkg-config tool'
 
 ! go list -export .
-stderr '^# example\n# \[pkg-config .*\]\n(.*\n)*Package .* not found'
+# 'Package .* not found appears' in pkg-config and pkgconf; while
+# 'could not find package .*' appears in u-config. See #68283.
+stderr '#^ example\n#pkg-config .*\n(.*\n)*(Package .* not found)|(could not find package .*)'
 
 -- go.mod --
 module example