Can't configure on OSX (nightly)

[yongqli]

After updating Xcode, running ./configure results in:

configure: error: bad APPLE CLANG version: 7.3.0, need >=7.0

 % clang --version
Apple LLVM version 7.3.0 (clang-703.0.29)
Target: x86_64-apple-darwin15.4.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

[durka]

looks like this will be fixed by #32425

[cryon]

This is still an issue with release 1.8.