pre-POSIX.1-2001 systems do not have <sys/select.h>

POSIX.1-2001 has declaration of select(2) in <sys/select.h>, but
in the previous version of SUS, it was declared in <sys/time.h>
(which is already included in git-compat-util.h).

This introduces NO_SYS_SELECT_H macro in the Makefile to be set
on older systems, to skip inclusion of <sys/select.h> that does
not exist on them.

We could check _POSIX_VERSION with 200112L and do this
automatically, but earlier it was reported that the approach
does not work well on some vintage of HP-UX.  Other systems may
get _POSIX_VERSION itself wrong.  At least for now, this manual
configuration is safer.
Signed-off-by: NRobert Schiele <rschiele@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Makefile

@@ -42,6 +42,8 @@ all::
 #
 # Define NO_MKDTEMP if you don't have mkdtemp in the C library.
 #
+# Define NO_SYS_SELECT_H if you don't have sys/select.h.
+#
 # Define NO_SYMLINK_HEAD if you never want .git/HEAD to be a symbolic link.
 # Enable it on Windows.  By default, symrefs are still used.
 #
@@ -635,6 +637,9 @@ ifdef NO_UNSETENV
 	COMPAT_CFLAGS += -DNO_UNSETENV
 	COMPAT_OBJS += compat/unsetenv.o
 endif
+ifdef NO_SYS_SELECT_H
+	BASIC_CFLAGS += -DNO_SYS_SELECT_H
+endif
 ifdef NO_MMAP
 	COMPAT_CFLAGS += -DNO_MMAP
 	COMPAT_OBJS += compat/mmap.o

git-compat-util.h

@@ -68,7 +68,9 @@
 #include <sys/poll.h>
 #include <sys/socket.h>
 #include <sys/ioctl.h>
+#ifndef NO_SYS_SELECT_H
 #include <sys/select.h>
+#endif
 #include <assert.h>
 #include <regex.h>
 #include <netinet/in.h>