[binutils-gdb] btrace: fix test build error in gdb.btrace/instruction_history.c

[sergiodj+buildbot at sergiodj dot net]

*** TEST RESULTS FOR COMMIT e26b7e41652e288dfdb4c48121bba470c4774150 ***

Author: Markus Metzger <markus.t.metzger@intel.com>
Branch: master
Commit: e26b7e41652e288dfdb4c48121bba470c4774150

btrace: fix test build error in gdb.btrace/instruction_history.c

On systems with a newer version of GCC the gdb.btrace/instruction_history.exp
test fails to build like this:

    Running .../gdb.btrace/instruction_history.exp ...
    gdb compile failed, .../gdb.btrace/instruction_history.c:
    In function 'main': .../gdb.btrace/instruction_history.c:24:3: warning:
    implicit declaration of function 'loop' [-Wimplicit-function-declaration]
       loop ();
       ^

Declare loop to fix it.

testsuite/
	* gdb.btrace/instruction_history.c (loop): Add declaration.