[PATCH] Avoid spurious gcc warning in debugger.c

[Daniel Kahn Gillmor <dkg@fifthhorseman.net>]

Without this patch, gcc 8.2.0-7 complains:

debugger.c: In function ‘debugger_is_active’:
debugger.c:40:24: warning: passing argument 2 to restrict-qualified parameter aliases with argument 1 [-Wrestrict]
     if (readlink (buf, buf, sizeof (buf)) != -1 &&
                   ~~~  ^~~

This is pretty silly, but it seems simplest to just avoid passing the
same buffer to readlink as both pathname and buf.
---
 debugger.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/debugger.c b/debugger.c
index 5cb38ac4..0febf170 100644
--- a/debugger.c
+++ b/debugger.c
@@ -32,13 +32,14 @@ bool
 debugger_is_active (void)
 {
     char buf[1024];
+    char buf2[1024];
 
     if (RUNNING_ON_VALGRIND)
 	return true;
 
     sprintf (buf, "/proc/%d/exe", getppid ());
-    if (readlink (buf, buf, sizeof (buf)) != -1 &&
-	strncmp (basename (buf), "gdb", 3) == 0)
+    if (readlink (buf, buf2, sizeof (buf2)) != -1 &&
+	strncmp (basename (buf2), "gdb", 3) == 0)
     {
 	return true;
     }
-- 
2.19.0