Relax gdb.compile/compile.exp to match the address printed for frame

One test in gdb.compile/compile.exp passes on one fedora builder,

 bt
 #0  0x00007ffff7ff43f6 in _gdb_expr (__regs=0x7ffff7ff2000) at gdb
 command line:1^M
 #1  <function called from gdb>^M
 #2  main () at /home/gdb-buildbot/fedora-x86-64-1/fedora-x86-64/build/gdb/testsuite/../../../binutils-gdb/gdb/testsuite/gdb.compile/compile.c:106^M
 (gdb) PASS: gdb.compile/compile.exp: bt

but fails on my machine with gcc trunk,

 bt^M
 #0  _gdb_expr (__regs=0x7ffff7ff3000) at gdb command line:1^M
 #1  <function called from gdb>^M
 #2  main () at gdb/testsuite/gdb.compile/compile.c:106^M
 (gdb) FAIL: gdb.compile/compile.exp: bt

The test should be tweaked to match both cases (pc in the start of line
vs pc in the middle of line).  Note that I am not clear that why libcc1
emits debug info this way so that the address is in the middle of line.

gdb/testsuite:

2018-01-17  Yao Qi  <yao.qi@linaro.org>

	* gdb.compile/compile.exp: Match the address printed for
	frame in the output of command "bt".

Author: Yao Qi

gdb/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2018-01-17  Yao Qi  <yao.qi@linaro.org>
+
+	* gdb.compile/compile.exp: Match the address printed for
+	frame in the output of command "bt".
+
 2018-01-15  Tom Tromey  <tom@tromey.com>
 
 	* gdb.guile/scm-ports.exp (test_mem_port_rw): Use get_valueof to

gdb/testsuite/gdb.compile/compile.exp

@@ -139,8 +139,11 @@ gdb_test "compile code func_doesnotexist ();" "warning: Could not find symbol \"
 gdb_test "compile code *(volatile int *) 0 = 0;" \
     "The program being debugged was signaled while in a function called from GDB\\.\r\nGDB remains in the frame where the signal was received\\.\r\n.*" \
     "compile code segfault first"
-gdb_test "bt" \
-    "\r\n#0  \[^\r\n\]* in _gdb_expr \[^\r\n\]*\r\n#1  <function called from gdb>\r\n.*"
+gdb_test "bt" [multi_line \
+		   "#0  ($hex in )?_gdb_expr .*" \
+		   "#1  <function called from gdb>" \
+		   "#2  .*" \
+		  ]
 
 set test "p/x \$pc"
 set infcall_pc 0