I have been working on reviving an older open source project, and when I updated the architecture from $(ARCHS_STANDARD_32_BIT) to $(ARCHS_STANDARD), Xcode gave me a very long error with the title Apple LLVM 6.0 Error which ended with the line Command /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang failed with exit code 1. I tried undoing the architecture change, but it still gave the error when I ran it again.
The previous build worked perfectly, and the only changes that were made on the erroneous build were:
1) I moved the project to Dropbox
2) I changed the architecture
Here is the full error: http://pastebin.com/huLnWc7v
I was trying to compile ARM code as if it were ARM64. Since it's just an app and not an extension, I don't need to do that. So, under Project>Target>Build Settings> Architectures I changed the Architectures key I standard architectures, and the Valid Architectures key to armv7.