When linux-user/exit was introduced we failed to move the gprof
include at the same time. The CI didn't notice because it only builds
system emulation. Fix it for those that still find gprof useful.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Laurent Desnogues <laurent.desnogues@gmail.com>
Message-Id: <20190502092728.32727-1-alex.bennee@linaro.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>