s3/wscript: only check for F_SETLEASE being available at compile time

s3/wscript: only check for F_SETLEASE being available at compile time

F_GETLEASE/F_SETLEASE are available (at least) since Linux 2.4.0 from
2002.

We also should not have the configure check depend on the filesystem
we find at build time. It's very common that the build-environment is
much more restricted than the runtime-environment will be.

As a history we had this check on Samba 3.6:

 AC_CACHE_CHECK([for Linux kernel oplocks],samba_cv_HAVE_KERNEL_OPLOCKS_LINUX,[
 AC_TRY_RUN([
 #include <sys/types.h>
 #include <fcntl.h>
 #ifndef F_GETLEASE
 #define F_GETLEASE	1025
 #endif
 main() {
        int fd = open("/dev/null", O_RDONLY);
        return fcntl(fd, F_GETLEASE, 0) == -1;
 }
 ],
 samba_cv_HAVE_KERNEL_OPLOCKS_LINUX=yes,samba_cv_HAVE_KERNEL_OPLOCKS_LINUX=no,samba_cv_HAVE_KERNEL_OPLOCKS_LINUX=cross)])
 if test x"$samba_cv_HAVE_KERNEL_OPLOCKS_LINUX" = x"yes"; then
    AC_DEFINE(HAVE_KERNEL_OPLOCKS_LINUX,1,[Whether to use linux kernel oplocks])
 fi

which didn't depend on the filesystem.

Then we got a broken check introduced in Samba 4.0 (a copy of the
F_NOTIFY check):

 # Check for Linux kernel oplocks
 conf.CHECK_CODE('''
 #include <sys/types.h>
 #include <fcntl.h>
 #include <signal.h>
 #ifndef F_NOTIFY
 #define F_NOTIFY 1026
 #endif
 main() {
         exit(fcntl(open("/tmp", O_RDONLY), F_NOTIFY, 0) == -1 ?  1 : 0);
 }''', 'HAVE_KERNEL_OPLOCKS_LINUX', addmain=False, execute=True,
        msg="Checking for Linux kernel oplocks")

this got "fixed" in Samba 4.7 (and backports to 4.6, 4.5 and 4.4) into

 # Check for Linux kernel oplocks
 conf.CHECK_CODE('''
 #include <sys/types.h>
 #include <fcntl.h>
 #include <signal.h>
 #ifndef F_GETLEASE
 #define F_GETLEASE 1025
 #endif
 main() {
         exit(fcntl(open("/tmp", O_RDONLY), F_GETLEASE, 0) == -1 ?  1 : 0);
 }''', 'HAVE_KERNEL_OPLOCKS_LINUX', addmain=False, execute=True,
        msg="Checking for Linux kernel oplocks")

Lately it became dependend on the filesystem in the build-environment:

 # Check for Linux kernel oplocks
 conf.CHECK_CODE('''
 #include <sys/types.h>
 #include <fcntl.h>
 #include <signal.h>
 #ifndef F_GETLEASE
 #define F_GETLEASE 1025
 #endif
 main() {
       const char *fname="/tmp/oplock-test.txt";
       int fd = open(fname, O_RDWR|O_CREAT, 0644);
       int ret = fcntl(fd, F_SETLEASE, F_WRLCK);
       unlink(fname);
       return (ret == -1) ? 1 : 0;
 }''', 'HAVE_KERNEL_OPLOCKS_LINUX', addmain=False, execute=True,
        msg="Checking for Linux kernel oplocks")

Now we just check for F_SETLEASE being available in linux/fcntl.h.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>