shared: handle missing Xcode/CLT version.

Fixes https://github.com/Homebrew/homebrew-core/issues/3973.

1 files changed, 10 insertions, 1 deletions

diff --git a/Library/Homebrew/extend/os/mac/extend/ENV/shared.rb b/Library/Homebrew/extend/os/mac/extend/ENV/shared.rb
index a33747203..6bf7ea6f0 100644
--- a/Library/Homebrew/extend/os/mac/extend/ENV/shared.rb
+++ b/Library/Homebrew/extend/os/mac/extend/ENV/shared.rb
@@ -1,6 +1,15 @@
 module SharedEnvExtension
   def no_weak_imports?
     return false unless compiler == :clang
-    MacOS::Xcode.version >= "8.0" || MacOS::CLT.version >= "8.0"
+
+    if MacOS::Xcode.version && MacOS::Xcode.version < "8.0"
+      return false
+    end
+
+    if MacOS::CLT.version && MacOS::CLT.version < "8.0"
+      return false
+    end
+
+    true
   end
 end