Vulkan: Use LLVM shader compiler for BOTW on Linux + Mesa (#1857)

vulkan: use the right exit function when vulkan fails to initialize.

build: Link zstd explicitly (#1860)

unix: simplify the case-insensitivity algorithm

unix: check current working directory for case-insensitive relative paths when no more parents

unix: handle edge case where path does not exist

input: Fix bitwise operation for button mask (#1851)

coreinit: Log errors in OSUnlockMutex instead of debug asserts

GX2: Fix several missing/incorrect cmd reserve calls

GX2: Fix return type of GX2DrawDone

PPCRec: Fix eflags optimization

coreinit: Implement OSFatal

coreinit: Refactor OSScreen

coreinit: Improve vcprintf implementation

build: Remove unnecessary includes to improve compile times