Here are some step-by-step instructions for installing the latest Objective C (including libobjc2) on a fresh Ubuntu server 12.10. I have posted it to the Wiki in case anyone has edits.
# Objective C 2.0 installation
# On fresh install of Ubuntu 12.10 Server
# Patryk Laurent (http://pakl.net/)
# Dec 27, 2012
sudo aptitude install build-essential git subversion ninja cmake
svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm
cd llvm/tools
svn co http://llvm.org/svn/llvm-project/cfe/trunk clang
cd .. # Back to llvm directory
./configure --enable-optimized
make -j4 # Go off to prepare cup of coffee here.
export PATH=$PATH:~/llvm/Release+Asserts/bin # Add to .bashrc
export CC=clang # Add to .bashrc
clang -v
svn co http://svn.gna.org/svn/gnustep/modules/core
svn co http://svn.gna.org/svn/gnustep/libs/libobjc2/trunk libobjc2
cd core/make
./configure --enable-debug-by-default --with-layout=gnustep
make && sudo -E make install
. /usr/GNUstep/System/Library/Makefiles/GNUstep.sh # Add to .bashrc
sudo aptitude install gobjc # Otherwise we get "cc1obj not found
cd ../../libobjc2
mkdir build
cd build
cmake ..
make
sudo -E make install
cat > blocktest.m << EOF
#include <stdio.h>
int main() {
void (^hello)(void) = ^(void) {
printf("Hello, block!\n");
};
hello();
return 0;
}
EOF
clang `gnustep-config --objc-flags` `gnustep-config --objc-libs` -fobj-arc -fobjc-nonfragile-abi -fblocks -lobjc blocktest.m