[PATCH] testsuite: use cygpath to convert from Unix to Windows paths

[Simon Marchi]

When on a MinGW host, standard_output_file uses a regular expression to
convert Unix-style paths of the form "/c/foo" to "c:/foo".  This is
needed because the paths we pass to GDB (for example, with the "file"
command) need to be in the Windows form.

However, the regexp only works if your binutils-gdb repo is under a
`/[a-z]/...` path (the Unix paths mapping to Windows drives).
Presumably, that works if you clone the repo in Windows, then access it
through `/c/...`.

In my case, I've cloned the repository directly inside my MinGW shell,
so in /home/smarchi.  The regexp therefore doesn't work for me.  The
path doesn't get transformed, and the file command fails when running
any test:

    (gdb) file /home/smarchi/build/binutils-gdb/gdb/testsuite/outputs/gdb.arch/i386-bp_permanent/i386-bp_permanent
    /home/smarchi/build/binutils-gdb/gdb/testsuite/outputs/gdb.arch/i386-bp_permanent/i386-bp_permanent: No such file or directory.

A safer way to do this conversion would be to use the cygpath utility.
It can be used to convert any MinGW path into its Windows equivalent.

Note that despite originally coming from Cygwin, the cygpath utility is
distributed by mingw-w64 and can be used in that environment.

With this, the file command in the test succeeds:

    (gdb) file C:/msys64/home/smarchi/build/binutils-gdb/gdb/testsuite/outputs/gdb.arch/i386-bp_permanent/i386-bp_permanent
    Reading symbols from C:/msys64/home/smarchi/build/binutils-gdb/gdb/testsuite/outputs/gdb.arch/i386-bp_permanent/i386-bp_permanent...

gdb/testsuite/ChangeLog:

	* lib/gdb.exp (standard_output_file): Use cygpath to convert
	from Unix to Windows path.
---
 gdb/testsuite/lib/gdb.exp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
index 9614e8dc87cd..ac16e0e85c99 100644
--- a/gdb/testsuite/lib/gdb.exp
+++ b/gdb/testsuite/lib/gdb.exp
@@ -4899,8 +4899,10 @@ proc standard_output_file {basename} {
     file mkdir $dir
     # If running on MinGW, replace /c/foo with c:/foo
     if { [ishost *-*-mingw*] } {
-        set dir [regsub {^/([a-z])/} $dir {\1:/}]
+       set dir [exec cygpath --mixed "${dir}"]
+
     }
+
     return [file join $dir $basename]
 }
 
-- 
2.25.1