Make the default sysroot be "target:"

This commit makes GDB default to a sysroot of "target:".
One testcase needed updating as a result of this change.

gdb/ChangeLog:

	* main.c (captured_main): Set gdb_sysroot to "target:"
	if not otherwise set.

gdb/testsuite/ChangeLog:

	* gdb.base/break-probes.exp: Cope with "target:" sysroot.

gdb/ChangeLog

@@ -1,3 +1,8 @@
+2015-04-02  Gary Benson <gbenson@redhat.com>
+
+	* main.c (captured_main): Set gdb_sysroot to "target:"
+	if not otherwise set.
+
 2015-04-02  Gary Benson <gbenson@redhat.com>
 
 	* exec.c (exec_file_attach): Support "target:" filenames.

gdb/main.c

@@ -548,6 +548,12 @@ captured_main (void *data)
   gdb_sysroot = relocate_gdb_directory (TARGET_SYSTEM_ROOT,
 					TARGET_SYSTEM_ROOT_RELOCATABLE);
 
+  if (gdb_sysroot == NULL || *gdb_sysroot == '\0')
+    {
+      xfree (gdb_sysroot);
+      gdb_sysroot = xstrdup (TARGET_SYSROOT_PREFIX);
+    }
+
   debug_file_directory = relocate_gdb_directory (DEBUGDIR,
 						 DEBUGDIR_RELOCATABLE);
 

gdb/testsuite/ChangeLog

@@ -1,3 +1,7 @@
+2015-04-02  Gary Benson <gbenson@redhat.com>
+
+	* gdb.base/break-probes.exp: Cope with "target:" sysroot.
+
 2015-04-01  Sasha Smundak  <asmundak@google.com>
 
 	* gdb.python/py-unwind-maint.c: New file.

gdb/testsuite/gdb.base/break-probes.exp

@@ -66,6 +66,10 @@ if { $using_probes } {
 	}
     }
 
+    # GDB strips "target:" from the start of filenames
+    # when operating on the local filesystem
+    regsub "^target:" "$sysroot" "(target:)?" sysroot
+
     # Run til it loads our library
     set test "run til our library loads"
     set not_loaded_library 1