Fix powerpc build

Unlike other architectures which sanitize the LDFLAGS from the
environment in arch/<arch>/Makefile.  The powerpc Makefile
allows LDFLAGS to be passed through resulting in the following
build failure.

  /usr/bin/ld: unrecognized option '-Wl,-z,relro'

LDFLAGS is set in /usr/lib/rpm/redhat/macros by default.  Clear
the environment variable when building kmods for powerpc.

Additionally, now that ppc64le exists it's not longer safe to
assume a powerpc system is big endian.  Rely on the endianness
provided by the compiler.

Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #5856

lib/libspl/include/sys/isa_defs.h

@@ -98,10 +98,6 @@ extern "C" {
 #endif
 #endif
 
-#if !defined(_BIG_ENDIAN)
-#define	_BIG_ENDIAN
-#endif
-
 #define	_SUNOS_VTOC_16
 
 /* arm arch specific defines */

rpm/generic/zfs-kmod.spec.in

@@ -86,6 +86,11 @@ BuildRequires:             kmod-spl-devel = %{version}
 %global KmodsMetaRequires  spl-kmod
 %endif
 
+# LDFLAGS are not sanitized by arch/powerpc/Makefile (unlike other arches)
+%ifarch ppc ppc64 ppc64le
+%global __global_ldflags %{nil}
+%endif
+
 %if 0%{?fedora} >= 17
 %define prefix  /usr
 %endif

rpm/redhat/zfs-kmod.spec.in

@@ -21,6 +21,11 @@ Requires:       spl-kmod\n\
 Requires:       @PACKAGE@ = %{version}\n\
 Conflicts:      @PACKAGE@-dkms\n\n" > %{_sourcedir}/kmod-preamble)
 
+# LDFLAGS are not sanitized by arch/powerpc/Makefile (unlike other arches)
+%ifarch ppc ppc64 ppc64le
+%global __global_ldflags %{nil}
+%endif
+
 %description
 This package contains the ZFS kernel modules.