title: How to modify the command XCode uses for creating the precompiled header?
body: <p>I'm developing an iPhone application, and after making small changes to my code, when I tried to build I suddenly got the following build error when XCode tries to create precompiled header:</p>
  
  <p><pre><code>i686-apple-darwin10-gcc-4.2.1: n: No such file or directory
  Command /Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin/gcc-4.2 failed with exit code 1
  </pre></code></p>
  
  <p><br>
  From the build log I can see that the crashing line is the following:</p>
  
  <p><pre><code>ProcessPCH /var/folders/rM/rMuXVqLVH+8h38HuH1nVVU+++Tk/-Caches-/com.apple.Xcode.508/SharedPrecompiledHeaders/ProjectName_Prefix-gmsrnnethxkzvrgfurlstopfubtu/ProjectName_Prefix.pch.gch ProjectName_Prefix.pch normal i386 objective-c com.apple.compilers.gcc.4_2
  cd ProjectDir
  setenv LANG en_US.US-ASCII
  setenv PATH "/Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin:/Developer/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin"
  /Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin/gcc-4.2 -x objective-c-header -arch i386 -fmessage-length=0 -pipe -std=c99 -Wno-trigraphs -fpascal-strings -fasm-blocks -O0 -Wreturn-type -Wunused-variable -DDEBUG -D__IPHONE_OS_VERSION_MIN_REQUIRED=30200 -isysroot /Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator4.0.sdk -fvisibility=hidden -mmacosx-version-min=10.6 -gdwarf-2 -fobjc-abi-version=2 -fobjc-legacy-dispatch -iquote ProjectDir/build/ProjectName.build/Debug-iphonesimulator/ProjectName.build/ProjectName-generated-files.hmap -IProjectDir/build/ProjectName.build/Debug-iphonesimulator/ProjectName.build/ProjectName-own-target-headers.hmap -IProjectDir/build/ProjectName.build/Debug-iphonesimulator/ProjectName.build/ProjectName-all-target-headers.hmap -iquote ProjectDir/build/ProjectName.build/Debug-iphonesimulator/ProjectName.build/ProjectName-project-headers.hmap -FProjectDir/build/Debug-iphonesimulator -I/ProjectDir/build/Debug-iphonesimulator/include -I../three20/Build/Products/three20 -IProjectDir/build/ProjectName.build/Debug-iphonesimulator/ProjectName.build/DerivedSources/i386 -IProjectDir/build/ProjectName.build/Debug-iphonesimulator/ProjectName.build/DerivedSources n -c ProjectDir/ProjectName_Prefix.pch -o /var/folders/rM/rMuXVqLVH+8h38HuH1nVVU+++Tk/-Caches-/com.apple.Xcode.508/SharedPrecompiledHeaders/ProjectName_Prefix-gmsrnnethxkzvrgfurlstopfubtu/ProjectName_Prefix.pch.gch</p>
  
  <p>i686-apple-darwin10-gcc-4.2.1: n: No such file or directory
  Command /Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin/gcc-4.2 failed with exit code 1
  </pre></code>
  <br>
  For some reason there is suddenly term 'n' in the middle of the command (... /DerivedSources n -c ...) , and as far as I can tell it really does not belong there.
  <br>
  <br>
  I tried emptying XCode cache, cleaning the project, dependencies and precompiled headers, but when rebuilding I get the same error.
  <br><br>
  I also tried reverting all the changes I could think of that I had made after previous successful compile, but with no luck. I also tried reinstalling XCode (3.2.3) with no success. Other projects still seem to compile fine though.
  <br><br>
  How is it possible that this 'n' is suddenly appearing in the command, and is there any way for me to modify the line to get things working again?
  <br><br>
  Thanks in advance!</p>