cucumber-cpp: fix test on 10.13

[scpeters]

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---

The cucumber-cpp test has been failing in high sierra. The standard trick of ENV.delete("SDKROOT") wasn't quite enough, as it gave a bunch of errors like the following:

/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/cmath:322:9: error: no member named 'islessequal' in the global namespace
using ::islessequal;
      ~~^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/cmath:323:9: error: no member named 'islessgreater' in the global namespace
using ::islessgreater;
      ~~^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/cmath:324:9: error: no member named 'isunordered' in the global namespace
using ::isunordered;
      ~~^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/cmath:325:9: error: no member named 'isunordered' in the global namespace
using ::isunordered;
      ~~^

So I looked into it further and saw that there are a bunch of other environment variables that reference the 10.14 SDK in Xcode:

$ env | grep Xcode
LDFLAGS=-L/usr/local/lib -F/usr/local/Frameworks -Wl,-headerpad_max_install_names -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk
CPPFLAGS=-F/usr/local/Frameworks -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk
SDKROOT=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk
CPATH=/usr/local/include:/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk/usr/include
CMAKE_FRAMEWORK_PATH=/usr/local/Frameworks:/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk/System/Library/Frameworks
CXXFLAGS=-Os -w -pipe -march=core2 -mmacosx-version-min=10.13 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk
CFLAGS=-Os -w -pipe -march=core2 -mmacosx-version-min=10.13 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk
CMAKE_PREFIX_PATH=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk/usr
OBJCXXFLAGS=-Os -w -pipe -march=core2 -mmacosx-version-min=10.13 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk
OBJCFLAGS=-Os -w -pipe -march=core2 -mmacosx-version-min=10.13 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk

Since the 2nd failure seems to be related to C header files, I added ENV.delete("CPATH"), and that seems to be enough.

Perhaps this method will help with graph-tool and other 10.13 failures.

[scpeters]

I think bottle updates aren't needed, since this just updates the test.

[lembacon]

I think bottle updates aren't needed, since this just updates the test.

Agreed.