Currently, this fails with many tools, e.g.
$ clang -fembed-bitcode-marker -c -o test.o test.c
$ nm test.o
/Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/nm: test.o The file was not recognized as a valid object file
-fembed-bitcode-marker creates a LLVM,bitcode section consisting of a single byte. When reading the object file, IRObjectFile::findBitcodeInObject succeeds, causing SymbolicFile::createSymbolicFile to try to read the "bitcode" rather than using the outer Mach-O data - when then fails.
Fix this by making findBitcodeInObject return an error if the section size <= 1.