Make from top level errors out

[stephen-hawley]

This happens on the local machine but works on the build server.

stevehawley@Steves-MacBook-Pro binding-tools-for-swift % make
Checking system...
    Found macOS 11.2.3 (at least 10.15 is required)
        Deleted Xcode cache file: /var/folders/3p/4gz1q1wx383d8pp9q2j49x_h0000gn/T/com.apple.dt.Xcode.InstallCheckCache_CoreSim_20D91_12E262 (this is normal)
        Deleted Xcode cache file: /var/folders/3p/4gz1q1wx383d8pp9q2j49x_h0000gn/T/com.apple.dt.Xcode.InstallCheckCache_com.apple.pkg.CoreTypes.1450A6_20D91_12E262 (this is normal)
        Deleted Xcode cache file: /var/folders/3p/4gz1q1wx383d8pp9q2j49x_h0000gn/T/com.apple.dt.Xcode.InstallCheckCache_MobileDevice_20D91_12D4e (this is normal)
        Deleted Xcode cache file: /var/folders/3p/4gz1q1wx383d8pp9q2j49x_h0000gn/T/com.apple.dt.Xcode.InstallCheckCache_com.apple.pkg.CoreTypes.1420B27_20D91_12D4e (this is normal)
        Deleted Xcode cache file: /var/folders/3p/4gz1q1wx383d8pp9q2j49x_h0000gn/T/com.apple.dt.Xcode.InstallCheckCache_com.apple.pkg.MobileDeviceDevelopment_20D91_12E262 (this is normal)
        Deleted Xcode cache file: /var/folders/3p/4gz1q1wx383d8pp9q2j49x_h0000gn/T/com.apple.dt.Xcode.InstallCheckCache_MobileDevice_20D91_12E262 (this is normal)
        Deleted Xcode cache file: /var/folders/3p/4gz1q1wx383d8pp9q2j49x_h0000gn/T/com.apple.dt.Xcode.InstallCheckCache_com.apple.pkg.MobileDeviceDevelopment_20D91_12D4e (this is normal)
        Deleted Xcode cache file: /var/folders/3p/4gz1q1wx383d8pp9q2j49x_h0000gn/T/com.apple.dt.Xcode.InstallCheckCache_CoreSim_20D91_12D4e (this is normal)
    Found Xcode 12.4 in /Applications/Xcode_12.4.app
    You should have exactly CoreSimulator.framework version 732.18 (found 757.5). Execute './devops/automation/system-dependencies.sh --provision-xcode' to install the expected version.
    Found Mono 6.12.0.90 (at least 6.12.0.90 and not more than 6.12.0.90 is required)
    Found Xamarin.iOS 13.18.2.1 (at least 13.18.2.1 and not more than 13.18.2.1 is required)
    Found Xamarin.Mac 6.22.1.26 (at least 6.22.1.26 and not more than 6.22.1.26 is required)
    Found CMake 3.20.0 (at least 3.18.4 is required)
    Found OpenJDK 15.0.2 (at least 15.0.1 is required)
System check succeeded
Building Binding Tools For Swift 0.2.0.908
./devops/automation/build.sh
+ test -z ''
+ echo 'Variable BTFS_TOP is missing.'
Variable BTFS_TOP is missing.
+ exit 1
make: *** [all] Error 1