MacOS workaround: No suitable Xcode SDK or Command Line Tools installed.

[Hubert Feyrer <hubert%feyrer.de@localhost>]

FWIW, I've ended up with an environment[1] where pkgsrc doesn't work out 
of the box, giving me "No suitable Xcode SDK or Command Line Tools 
installed."

Apparently this is because OSX_VERSION (derived from "/usr/bin/xcrun 
--show-sdk-version") is not what is expected in "sw_vers -productVersion":

	promise% /usr/bin/xcrun --show-sdk-version
	10.14
	promise% sw_vers -productVersion
	10.13.6

A quick hack to align this is to put the following into mk.conf:

	# HF HACK:
	# work around "/usr/bin/xcrun --show-sdk-version"
	# giving something else than "sw_vers -productVersion"
	OSX_VERSION=10.14

I'm sure there is a better way to fix this, but at least this gets me a 
working pkgsrc again.

If someone wants to analyze this and needs more data, feel free to contact 
me.


 - Hubert




[1] My environment:

promise% uname -a
Darwin promise.local 17.7.0 Darwin Kernel Version 17.7.0: Wed Feb 27 
00:43:23 PST 2019; root:xnu-4570.71.35~1/RELEASE_X86_64 x86_64

promise% gcc -v
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr 
--with-gxx-include-dir=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/c++/4.2.1
Apple LLVM version 10.0.0 (clang-1000.11.45.5)
Target: x86_64-apple-darwin17.7.0
Thread model: posix
InstalledDir: 
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

Need more information? Feel free to ask!