[MONGOCRYPT-874] Refactor build scripts to use more standard environment variable controls for CMake

[vector-of-bool]

Refer: MONGOCRYPT-874

This changeset simplifies the build scripts by removing custom environment variables, as well as some legacy cruft that is no longer relevant. It can be viewed on a per-commit basis.

Summary

• 14682f5 Removes logic that sets -A and -T when invoking CMake. These are no longer relevant since we use Ninja on Windows and vs-env-run.ps1 sets the environment for us. Besides, the proper way to do that would be to use the CMAKE_GENERATOR_PLATFORM AND CMAKE_GENERATOR_TOOLSET environment variables to control the target for the VS (MSBuild) CMake generator.
• fb16f91 Tosses out EXTRA_CFLAGS in favor of using CFLAGS and CXXFLAGS, which are recognized by CMake to initialize CMAKE_C_FLAGS and CMAKE_CXX_FLAGS. These are standard across build tools.
• b0ae833 and 9238191 drop the MACOS_UNIVERSAL environment variable control in favor of CMake's standard CMAKE_OSX_ARCHITECTURES flag. The test case that asserts we generate a multi-arch binary remains.
• 4c1bd8f Drops juggling the -G flag and the use_ninja expansion/environment variable in favor of using the CMAKE_GENERATOR environment variable.
  • Ideally, the build scripts should be written agnostic of the CMake generator, but our custom Ninja-loading code still does some work here. When we eventually adopt uv to manage Ninja, the ensure-ninja.sh and related scripts should be removed and our build scripts should not acknowledge the generator.
• b3b3fef Significantly cleans up build_all.sh
  • We use environment variables to pass certain CMake controls: CMAKE_BUILD_TYPE, CMAKE_CONFIG_TYPE (controls the default for --build and ctest), CMAKE_INSTALL_PREFIX, and CMAKE_EXPORT_COMPILE_COMMANDS.
  • We rely much less on string splicing to form our command lines. The build_all.sh is now shellcheck-clean.
• d009ba5 Use CC and CXX to control the compiler executables, not by setting CMAKE_C_COMPILER and CMAKE_CXX_COMPILER.
• 8927fc0 Completely remove LIBMONGOCRYPT_EXTRA_CMAKE_FLAGS
• 208c8f1 Drop ADDITIONAL_CMAKE_FLAGS
• 83deb0b Drop the DEFAULT_BUILD_ONLY control. This didn't appear to be used anywhere.
• 3bd5e7a Pass --fresh in build_all.sh when we invoke CMake each time.
• 8df7cc7 Don't set -EHsc on Windows. This was incorrect because it should be checking for MSVC. It doesn't appear to have any effect on the build?
• d0743af Don't set MAKEFLAGS to control parallelism. CMake respects CMAKE_BUILD_PARALLEL_LEVEL environment variable to control parallelism regardless of the underlying build tool.

[eramongodb]

Curious: why prepend instead of append?

[vector-of-bool]

No reason at all, just how I happened to write it.