libgmp is the big number library.

Firstly, we need to make it build using the cross compiler.

Secondly, apply a small patch to the ARM assembly code, which is needed because
Apple ships a pre-historic version of the GNU assembler.

--- ghc-6.10.2.orig/gmp/Makefile	2009-03-31 06:13:16.000000000 +1300
+++ ghc-6.10.2/gmp/Makefile	2009-06-18 15:54:37.000000000 +1200
@@ -63,27 +63,41 @@
 stamp.gmp.static:
 	$(RM) -rf $(GMP_DIR) gmpbuild
 	$(TAR) -zxf $(GMP_TARBALL)
+	cat iphone.patch | (cd $(GMP_DIR) && patch -p1)
 	mv $(GMP_DIR) gmpbuild
 	chmod +x ln
 	(set -o igncr 2>/dev/null) && set -o igncr; export SHELLOPTS; \
 	    PATH=`pwd`:$$PATH; \
 	    export PATH; \
 	    cd gmpbuild && \
-	    CC=$(WhatGccIsCalled) $(SHELL) configure \
-	          --enable-shared=no --host=$(PLATFORM) --build=$(PLATFORM)
+	        CC="$(TARGET_GCC)" \
+                AR="$(TARGET_AR)" \
+                LD="$(TARGET_LD)" \
+                CFLAGS="$(TARGET_CFLAGS)" \
+                CPPFLAGS="$(TARGET_CPPFLAGS)" \
+                LDFLAGS="$(TARGET_LDFLAGS)" \
+                $(SHELL) configure \
+                  --enable-shared=no --host=$(PLATFORM)
 	touch $@
 
 stamp.gmp.shared:
 	$(RM) -rf $(GMP_DIR) gmpbuild-shared
 	$(TAR) -zxf $(GMP_TARBALL)
+	cat iphone.patch | (cd $(GMP_DIR) && patch -p1)
 	mv $(GMP_DIR) gmpbuild-shared
 	chmod +x ln
 	(set -o igncr 2>/dev/null) && set -o igncr; export SHELLOPTS; \
 	    PATH=`pwd`:$$PATH; \
 	    export PATH; \
 	    cd gmpbuild-shared && \
-	    CC=$(WhatGccIsCalled) $(SHELL) configure \
-	          --enable-shared=yes --disable-static --host=$(PLATFORM) --build=$(PLATFORM)
+	        CC="$(TARGET_GCC)" \
+                AR="$(TARGET_AR)" \
+                LD="$(TARGET_LD)" \
+                CFLAGS="$(TARGET_CFLAGS)" \
+                CPPFLAGS="$(TARGET_CPPFLAGS)" \
+                LDFLAGS="$(TARGET_LDFLAGS)" \
+                $(SHELL) configure \
+	          --enable-shared=yes --disable-static --host=$(PLATFORM)
 	touch $@
 
 gmp.h: stamp.gmp.static
--- ghc-6.10.2.orig/gmp/iphone.patch	1970-01-01 12:00:00.000000000 +1200
+++ ghc-6.10.2/gmp/iphone.patch	2009-06-18 15:54:37.000000000 +1200
@@ -0,0 +1,11 @@
+--- gmpbuild.orig/mpn/arm/invert_limb.asm	2006-03-15 04:57:54.000000000 +1300
++++ gmpbuild/mpn/arm/invert_limb.asm	2009-04-14 15:27:40.000000000 +1200
+@@ -29,7 +29,7 @@
+ 	stmfd	sp!, {r4, lr}
+ 	mov	r3, d, lsr #23
+ 	sub	r3, r3, #256
+-	add	r2, pc, #invtab-.-8
++	adr	r2, invtab
+ 	mov	r3, r3, lsl #1
+ 	ldrh	r1, [r2, r3]		C get initial approximation from table
+ 	mov	r2, r1, lsl #6		C start iteration 1