Fix NEON detection on ARM linux

That returns aarch64 instead of arm64 in CMAKE_SYSTEM_PROCESSOR (per uname -p). We should be able to try detection on any platform now, though, so let's not hardcode those rules.

CMakeLists.txt

@@ -76,14 +76,11 @@ add_library(blake3 OBJECT src/blake3/blake3.c src/blake3/blake3_dispatch.c src/b
 set_property(TARGET blake3 APPEND PROPERTY COMPILE_FLAGS "-O3")
 set_property(TARGET blake3 PROPERTY C_STANDARD 99)
 
-if(CMAKE_SYSTEM_PROCESSOR STREQUAL "arm64")
-	CHECK_C_SOURCE_COMPILES("#include <arm_neon.h>\nint main() { return 0; }" COMPILER_SUPPORTS_NEON)
-else()
-	CHECK_C_COMPILER_FLAG("-msse2" COMPILER_SUPPORTS_SSE2)
-	CHECK_C_COMPILER_FLAG("-msse4.1" COMPILER_SUPPORTS_SSE_4_1)
-	CHECK_C_COMPILER_FLAG("-mavx2" COMPILER_SUPPORTS_AVX2)
-	CHECK_C_COMPILER_FLAG("-mavx512f -mavx512vl" COMPILER_SUPPORTS_AVX512)
-endif()
+CHECK_C_SOURCE_COMPILES("#include <arm_neon.h>\nint main() { return 0; }" COMPILER_SUPPORTS_NEON)
+CHECK_C_COMPILER_FLAG("-msse2" COMPILER_SUPPORTS_SSE2)
+CHECK_C_COMPILER_FLAG("-msse4.1" COMPILER_SUPPORTS_SSE_4_1)
+CHECK_C_COMPILER_FLAG("-mavx2" COMPILER_SUPPORTS_AVX2)
+CHECK_C_COMPILER_FLAG("-mavx512f -mavx512vl" COMPILER_SUPPORTS_AVX512)
 
 if(COMPILER_SUPPORTS_NEON)
 	target_sources(blake3 PRIVATE "src/blake3/blake3_neon.c")