cmd/go: skip TestScript/list_goroot_symlink on darwin

The list_goroot_symlink test relies on fsys.Walk (and ultimately
syscall.Lstat) conforming to POSIX pathname resolution semantics.
POSIX requires that symlinks ending in a slash be fully resolved,
but it appears that lstat in current darwin kernels does not fully
resolve the last pathname component when it is a symlink to a symlink.

For #59586.
For #35678.

Change-Id: I37526f012ba94fa1796b33109a41c3226c967d3e
Reviewed-on: https://go-review.googlesource.com/c/go/+/484216
Run-TryBot: Bryan Mills <bcmills@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Auto-Submit: Bryan Mills <bcmills@google.com>
TryBot-Bypass: Bryan Mills <bcmills@google.com>

Author: Bryan C. Mills

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

@@ -6,6 +6,7 @@
 
 [short] skip 'copies the cmd/go binary'
 [!symlink] skip 'tests symlink-specific behavior'
+[GOOS:darwin] skip 'Lstat on darwin does not conform to POSIX pathname resolution; see #59586'
 
 # Ensure that the relative path to $WORK/lib/goroot/src from $PWD is a different
 # number of ".." hops than the relative path to it from $WORK/share/goroot/src.