When the NO_MKSTEMPS build variable is not set, the gitmkstemps
function is dead code. Use a preprocessor conditional to only include
the definition when needed.
Noticed by sparse. ("'gitmkstemps' was not declared. Should it be
static?")
Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk> Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>