build: fix Clang warnings

[rr-]

Checklist

• I have read the coding conventions
• I have added a changelog entry about what my pull request accomplishes, or it is an internal change
• I have added a readme entry about my new feature or OG bug fix, or it is a different change

Description

Further cleanup for #2226.

• Removes unused SPRITE_FLAG enums that I mistakenly looked up from TR2Main.

• Removes 0 from all empty struct initializers. This syntax is supported since ISO C23 (see 6.7.10 Initialization):

  braced-initializer:
                      { }
                      { initializer-list }
                      { initializer-list , }
  

  An empty brace pair ({}) is called an empty initializer and is referred to as empty initialization

  Unfortunately we need -Wno-gnu-empty-initializer for Clang to recognize this.

• Removes ambiguity in controller binding declarations (specifically, the bind union) by introducing separate macros for BT_BUTTON and BT_AXIS.

• Adds -Wno-gnu-binary-literal to get Clang to recognize the binary literals, though this is also a part of the C23 standard. This has been fixed upstream, but has not yet found its way into our toolchain. Ref: [clang] Binary literals are flagged as a GNU extension even when compiling in C23 mode llvm/llvm-project#72017

• Adds -Wno-gnu-zero-variadic-macro-arguments' to get the GLYPH_DEFINE macro to not produce invalid warnings. Passing zero variadic macro arguments is valid since C23. This has been fixed upstream, but has not yet found its way into our toolchain. Ref: Zero variable arguments should be allowed in C23 llvm/llvm-project#84495

• Fixes one case of an unitialized variable usage.

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• TR1X-4.7.1-369-g84d22c9-linux.zip
• TR1X-4.7.1-369-g84d22c9-mac.zip
• TR1X-4.7.1-369-g84d22c9-win.zip
• TR1X-4.7.1-369-g84d22c9-win-installer.zip
• TR2X-0.8-147-g84d22c9-linux.zip
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