build-unit-test-docker: utilize https for llvm install

Some of our internal networks have started to completely block http.
This llvm.sh script utilizes a http address by default for some wget
commands. An issue[1] has been opened on the llvm project but for now
just utilize a workaround to tell the script to use https.

Tested:
- Confirmed script now correctly builds in environment without http
  support

[1]: https://github.com/llvm/llvm-project/issues/163216

Change-Id: Iadcb05e94480c3a91dc65c33e41f274ac545fd99
Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
diff --git a/scripts/build-unit-test-docker b/scripts/build-unit-test-docker
index 6ff7c8e..9887f78 100755
--- a/scripts/build-unit-test-docker
+++ b/scripts/build-unit-test-docker
@@ -959,7 +959,7 @@
     update-alternatives --install /usr/bin/cpp cpp /usr/bin/cpp-15 15
 
 # Set up LLVM apt repository.
-RUN bash -c "$(wget -O - https://apt.llvm.org/llvm.sh)" -- 21
+RUN bash -c "$(wget -O - https://apt.llvm.org/llvm.sh)" -- 21 -m https://apt.llvm.org
 
 # Install extra clang tools
 RUN apt-get install -y \