Update docker image of osxcross to latest requirements.

Building osxcross is somewhat problematic because the versions
are not fixed and reproducibility of making this docker file
can be problematic. For example new versions of cmake, etc
make be needed. TODO Is there a way to fix the version of
osxcross so that we can rebuild reliably?

docker/cdt-infra-build-macos-sdk/ubuntu-18.04/Dockerfile

@@ -3,11 +3,23 @@ FROM ubuntu:18.04
 
 RUN apt-get update
 RUN apt-get install -y clang make build-essential
-RUN apt-get install -y libssl-dev lzma-dev liblzma-dev libxml2-dev git cmake patch python cpio bzip2 xz-utils libbz2-dev
+RUN apt-get install -y libssl-dev lzma-dev liblzma-dev libxml2-dev git patch python cpio bzip2 xz-utils libbz2-dev
+
+# cmake in Ubuntu is too old to build osxcross, therefore
+# use this version
+RUN apt-get install -y curl
+RUN curl -fsSL https://github.com/Kitware/CMake/releases/download/v3.29.2/cmake-3.29.2-linux-x86_64.tar.gz | tar xzf - -C /usr/share
+ENV PATH="/usr/share/cmake-3.29.2-linux-x86_64/bin:${PATH}"
+
 
 # Xcode_13.1.xip needs to be downloaded from
 # https://developer.apple.com/download/all/?q=xcode - specically:
 ARG Xcodexip=Xcode_13.1.xip
+### Building osxcross is somewhat problematic because the versions
+### are not fixed and reproducibility of making this docker file
+### can be problematic. For example new versions of cmake, etc
+### make be needed. TODO Is there a way to fix the version of 
+### osxcross so that we can rebuild reliably?
 WORKDIR /opt
 COPY ${Xcodexip} /opt/${Xcodexip}
 RUN git clone https://github.com/tpoechtrager/osxcross.git