title: Can't compile libjpeg-turbo for iOS on Xcode 5 / Clang toolchain with SIMD / NEON support
body: <p>Looks like with Xcode 5 and the removal of LLVM-GCC-4.2 and its replacement by Clang, building libjpeg-turbo for iOS devices now fails during the compilation of NEON support.</p>
  
  <p>Configure step:</p>
  
  <pre><code>export PLATFORM="iPhoneOS"
  export IPHONE_SDK="7.0"
  export IPHONE_MIN_VERSION="5.0"
  
  export DEVELOPER=`xcode-select --print-path`
  export DEVROOT="${DEVELOPER}/Platforms/${PLATFORM}.platform/Developer"
  export SDKROOT="${DEVROOT}/SDKs/${PLATFORM}${IPHONE_SDK}.sdk"
  export CC=`xcrun -find gcc`
  export LD=`xcrun -find ld`
  export IOS_CFLAGS="-arch armv7"
  export CFLAGS="-O3 ${IOS_CFLAGS} -isysroot ${SDKROOT}"
  export LDFLAGS="${IOS_CFLAGS} -isysroot ${SDKROOT}"
  export CPPFLAGS="${CFLAGS}"
  export CFLAGS="${CFLAGS} -miphoneos-version-min=${IPHONE_MIN_VERSION}"
  
  ./configure --with-jpeg8 --host arm-apple-darwin --enable-static --disable-shared
  ...
  checking if we have SIMD optimisations for cpu type... yes (arm)
  checking if the assembler is GNU-compatible and can be used... yes
  ...
  </code></pre>
  
  <p>Build step:</p>
  
  <pre><code>make -j4
      /Applications/Xcode.app/Contents/Developer/usr/bin/make  all-recursive
  Making all in java
  echo timestamp &gt; classnodist_noinst.stamp
  Making all in simd
  /Applications/Xcode.app/Contents/Developer/usr/bin/gcc -E -I.. -I../simd ./jsimdcfg.inc.h | grep -E "^[\;%]|^\ %" | sed 's%_cpp_protection_%%' | sed 's@% define@%define@g' &gt; jsimdcfg.inc
  /Applications/Xcode.app/Contents/Developer/usr/bin/make  all-am
  if /bin/sh ../libtool --mode=compile --tag=CC /Applications/Xcode.app/Contents/Developer/usr/bin/gcc -DHAVE_CONFIG_H -I. -I. -I.. -I..  -I..  -O3 -arch armv7 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS7.0.sdk  -O3 -arch armv7 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS7.0.sdk -miphoneos-version-min=5.0 -MT jsimd_arm.lo -MD -MP -MF ".deps/jsimd_arm.Tpo" -c -o jsimd_arm.lo jsimd_arm.c; \
      then mv -f ".deps/jsimd_arm.Tpo" ".deps/jsimd_arm.Plo"; else rm -f ".deps/jsimd_arm.Tpo"; exit 1; fi
  /bin/sh ../libtool --mode=compile gas-preprocessor.pl /Applications/Xcode.app/Contents/Developer/usr/bin/gcc  -O3 -arch armv7 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS7.0.sdk -miphoneos-version-min=5.0 -c -o jsimd_arm_neon.lo jsimd_arm_neon.S
  libtool: compile: unable to infer tagged configuration
  libtool: compile: specify a tag with `--tag'
  make[3]: *** [jsimd_arm_neon.lo] Error 1
  make[3]: *** Waiting for unfinished jobs....
   /Applications/Xcode.app/Contents/Developer/usr/bin/gcc -DHAVE_CONFIG_H -I. -I. -I.. -I.. -I.. -O3 -arch armv7 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS7.0.sdk -O3 -arch armv7 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS7.0.sdk -miphoneos-version-min=5.0 -MT jsimd_arm.lo -MD -MP -MF .deps/jsimd_arm.Tpo -c jsimd_arm.c -o jsimd_arm.o
  make[2]: *** [all] Error 2
  make[1]: *** [all-recursive] Error 1
  make: *** [all] Error 2
  </code></pre>
  
  <p>Any idea how to fix this? The build succeeds if disabling SIMD support but that's obviously not great.</p>