arch/sparc: add absic support

Add support for building SPARC targeted toolchain.
With this patch I have built a working sparc V8 (32 toolchain).

Testing shows that not all gcc versions works well:
4.4.1            OK  (kernel builds and the final kernel can boot)
4.4.2            Not tested
4.4.3            Not tested
4.4.4            BAD (Kernel can build but fails during boot)
4.4.5            BAD (Kernel can build but fails during boot)
4.5.1            BAD (Build fails with a spill related ICE - http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35664)
4.5.2            OK  (kernel builds and boots)

I have successfully been using the 4.5.2 version for a few months.

This patch does not add support for the LEON variant.
That may come later.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
[yann.morin.1998@anciens.enib.fr: for 32-bit, default CT_TARGET_ARCH is OK]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

config/arch/sparc.in

@@ -0,0 +1,13 @@
+# SPARC specific config options
+
+config ARCH_sparc
+    select ARCH_SUPPORTS_32
+    select ARCH_SUPPORTS_64
+    select ARCH_DEFAULT_32
+    select ARCH_USE_MMU
+    select ARCH_SUPPORT_CPU
+    select ARCH_SUPPORT_TUNE
+    help
+      The SUN SPARC architecture, as defined by:
+        32 bit: http://www.sparc.org/standards/V8.pdf
+        64 bit: http://www.sparc.org/standards/SPARCV9.pdf

scripts/build/arch/sparc.sh

@@ -0,0 +1,8 @@
+# Compute sparc-specific values
+CT_DoArchTupleValues() {
+    # That's the only thing to override
+    if [ "${CT_ARCH_64}" = "y" ]; then
+        CT_TARGET_ARCH="${CT_ARCH}64"
+    fi
+
+}