Updates for clean builds across iOS / macOS / Android (all platforms)

[andybrucenet]

We will be integrating oqs-provider with our specific static liboqs / openssl builds. This fork ensures that we can build static oqs-provider libraries for all platforms.

Specific changes:

• Ignore 'build' and 'tmp' folders from git
• Modify CMakeLists.txt per https://stackoverflow.com/a/73886192/1318024 (Android Toolchain problems)
• Permit explicit setting for liboqs header via optional CMake var LIBOQS_INCLUDE_DIR
• #include <stdint.h> to ensure that uint64_t and friends are defined.
• Generic wrapper build script for creating builds for all the macOS / iOS / Android platforms we use. The build script requires that liboqs is cloned and built.

The required changes include the <stdint.h> include and the CMakeLists mods.

There are no known issues hit by this PR.