[docker] Fix LLVM_EXTERNAL_PROJECTS cmake variable value

Summary:
LLVM_ENABLE_PROJECTS expects a semicolon separated project list.

Fixes PR38158.

Reviewers: ilya-biryukov

Reviewed By: ilya-biryukov

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D49712

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@337842 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed