[fix] prebuild set CMAKE_PREFIX_PATH properly

[TingDaoK]

Issue #, if available:

• sometimes the prebuild uses a random path as the build path (Maybe inherent from the main cmake project??)
• eg: https://github.com/awslabs/aws-crt-cpp/actions/runs/11280312454/job/31373012913?pr=665#step:3:902
• After the adding the -B explicit as the build path fixes the issue:

 -- XXXXXXXXXXXX depBinaryDir /root/aws-crt-cpp/build/aws-crt-cpp/deps/S2N
CMake Warning:
  Ignoring extra path from command line:

   "/root/aws-crt-cpp/build/install"

cmakeCommand /usr/bin/cmake;-S;/root/aws-crt-cpp/crt/s2n;
-DCMAKE_BUILD_TYPE=RelWithDebInfo;
-DCMAKE_PREFIX_PATH=/root/aws-crt-cpp/build/aws-crt-cpp/deps/AWSLC/install/;/root/aws-crt-cpp/build/install;
-DCMAKE_INSTALL_PREFIX=/root/aws-crt-cpp/build/aws-crt-cpp/deps/S2N/install;
-DCMAKE_INSTALL_RPATH=;
-DBUILD_SHARED_LIBS=;
-DUNSAFE_TREAT_WARNINGS_AS_ERRORS=OFF;
-DBUILD_TESTING=OFF

After more digging

• It's not random, it's from some other CMAKE_PREFIX_PATH
• We add the new install path to the CMAKE_PREFIX_PATH, so the CMAKE_PREFIX_PATH is now a list
• We add CMAKE_PREFIX_PATH variable into the list of args to call for Cmake execute_process, it seems like based on the version of CMAKE, cmake sometimes confuses about those values. And treat the second value in the CMAKE_PREFIX_PATH list as a separate args for cmake to take.
• You can see -DCMAKE_PREFIX_PATH=/root/aws-crt-cpp/build/aws-crt-cpp/deps/AWSLC/install/;/root/aws-crt-cpp/build/install; I assume some version of cmake just took it as -DCMAKE_PREFIX_PATH=/root/aws-crt-cpp/build/aws-crt-cpp/deps/AWSLC/install/ and /root/aws-crt-cpp/build/install
• I tried a lot different way to set the CMAKE_PREFIX_PATH properly, and MOST failed.
• I have to set the environment variable of CMAKE_PREFIX_PATH instead of passing it to as the commend line args for Cmake, which seems to work.

Description of changes:

• Set the CMAKE_PREFIX_PATH as environment variables incase of multiple cmake prefix path needs to be set,
• With the fix, https://github.com/awslabs/aws-crt-cpp/actions/runs/11283228222/job/31382255479?pr=665 works
• Updated to use the escape for the string to pass in

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.84%. Comparing base (6978946) to head (7310e92).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1154   +/-   ##
=======================================
  Coverage   83.84%   83.84%           
=======================================
  Files          57       57           
  Lines        5992     5993    +1     
=======================================
+ Hits         5024     5025    +1     
  Misses        968      968           

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[graebm]

changing an environment variable seems like trouble
try to find a way to continue passing this as arguments
can do something to convince cmake more strongly that we want to treat this as a string, not a list

[graebm]

list(JOIN) is cmake 3.12+