xtensa: fix endianness support

To build uClibc correctly we need correct endianness selected in the
crosstool-NG. Xtensa cores may be little- or big-endian, but this
property is static. The toolchain knows the core endianness and doesn't
need options to select it.
Enable ARCH_SUPPORTS_BOTH_ENDIAN and select LE by default. Specify empty
CT_ARCH_ENDIAN_CFLAG so that -m{big,little}-endian don't get added to
the TARGET_CFLAGS, as it's not supported by gcc. Specify empty
CT_ARCH_ENDIAN_LDFLAG so that -EB/-EL don't get added to the
TARGET_LDFLAGS as they are ignored. Select big-endian in the example
xtensa-unknown-linux-uclibc configuration.

This fixes uClibc toolchain build for little-endian cores.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

config/arch/xtensa.in

@@ -1,6 +1,8 @@
 # xtensa specific configuration file
 
 ## select ARCH_SUPPORTS_32
+## select ARCH_SUPPORTS_BOTH_ENDIAN
+## select ARCH_DEFAULT_LE
 ## select ARCH_SUPPORTS_BOTH_MMU
 ## select ARCH_DEFAULT_HAS_MMU
 ##

samples/xtensa-unknown-linux-uclibc/crosstool.config

@@ -1,6 +1,7 @@
 CT_LOCAL_TARBALLS_DIR="${HOME}/src"
 CT_SAVE_TARBALLS=y
 CT_LOG_EXTRA=y
+CT_ARCH_BE=y
 CT_ARCH_xtensa=y
 CT_KERNEL_linux=y
 CT_LIBC_uClibc=y

scripts/build/arch/xtensa.sh

@@ -3,6 +3,8 @@
 CT_DoArchTupleValues() {
     # The architecture part of the tuple:
     CT_TARGET_ARCH="${CT_ARCH}${CT_ARCH_SUFFIX}"
+    CT_ARCH_ENDIAN_CFLAG=""
+    CT_ARCH_ENDIAN_LDFLAG=""
     # The system part of the tuple:
     case "${CT_LIBC}" in
         *glibc)   CT_TARGET_SYS=gnu;;