apr: add configure vars and caches

apr's configure script uses lots of AC_TRY_RUNs and when cross-compiling
needs a leg-up. This commit adds more configure variables (and removes
one, too).

Notable changes:

 - apr_cv_use_lfs64=yes is removed (again) after having a discussion
   about it with the musl developers. The conclusion was that
   _LARGEFILE64_SOURCE is a horrible thing that we don't want and should
   avoid (hence the removal of the variable, because defining
   _LARGEFILE64_SOURCE is all it does).
 - ap_cv_atomic_builtins is set to "yes" for 64-bit platforms. If
   anybody is interested in enabling this for other targets feel free to
   send a patch after testing it.
 - configure doesn't add -lpthread to LIBS when cross-compiling. This is
   not a problem for musl but might be for other libcs. This commit adds
   to related variable.
 - configure caches are added (via patches) for strerror and /dev/zero
   mmap tests. The former fixes a warning on musl (where strerror
   returns int instead of a pointer) and the latter is required for
   pthread pshared mutex apr_lock implementation and cannot be detected
   during cross-compile either.

Signed-off-by: Sebastian Kemper <sebastian_ml@gmx.net>

libs/apr/patches/303-add-cache-for-mmap-zero.patch

@@ -0,0 +1,25 @@
+--- a/configure.in
++++ b/configure.in
+@@ -1191,8 +1191,9 @@ AC_CHECK_FILE(/dev/zero)
+ # Not all systems can mmap /dev/zero (such as HP-UX).  Check for that.
+ if test "$ac_cv_func_mmap" = "yes" &&
+    test "$ac_cv_file__dev_zero" = "yes"; then
+-    AC_MSG_CHECKING(for mmap that can map /dev/zero)
+-    AC_TRY_RUN([
++    AC_CACHE_CHECK([for mmap that can map /dev/zero],
++    [ac_cv_mmap__dev_zero],
++    [AC_TRY_RUN([
+ #include <sys/types.h>
+ #include <sys/stat.h>
+ #include <fcntl.h>
+@@ -1215,9 +1216,7 @@ if test "$ac_cv_func_mmap" = "yes" &&
+             return 3;
+         }
+         return 0;
+-    }], [], [ac_cv_file__dev_zero=no], [ac_cv_file__dev_zero=no])
+-
+-    AC_MSG_RESULT($ac_cv_file__dev_zero)
++    }], [], [ac_cv_file__dev_zero=no], [ac_cv_file__dev_zero=no])])
+ fi
+ 
+ # Now we determine which one is our anonymous shmem preference.