cmake: Remove ENABLE_AVX2 from bitcoin-build-config.h

`ENABLE_AVX2` is already conditionally defined for the `bitcoin_crypto`
target, so defining it in `bitcoin-build-config.h` is redundant.

cmake/bitcoin-build-config.h.in

@@ -32,9 +32,6 @@
 /* Define this symbol to build code that uses ARMv8 SHA-NI intrinsics */
 #cmakedefine ENABLE_ARM_SHANI 1
 
-/* Define this symbol to build code that uses AVX2 intrinsics */
-#cmakedefine ENABLE_AVX2 1
-
 /* Define if external signer support is enabled */
 #cmakedefine ENABLE_EXTERNAL_SIGNER 1
 

cmake/introspection.cmake

@@ -184,7 +184,6 @@ if(NOT MSVC)
     " HAVE_AVX2
     CXXFLAGS ${AVX2_CXXFLAGS}
   )
-  set(ENABLE_AVX2 ${HAVE_AVX2})
 
   # Check for x86 SHA-NI intrinsics.
   set(X86_SHANI_CXXFLAGS -msse4 -msha)

test/lint/test_runner/src/main.rs

@@ -619,7 +619,6 @@ fn lint_includes_build_config() -> LintResult {
                     // These are exceptions which don't use bitcoin-build-config.h, rather CMakeLists.txt adds
                     // these cppflags manually.
                     ":(exclude)src/crypto/sha256_arm_shani.cpp",
-                    ":(exclude)src/crypto/sha256_avx2.cpp",
                     ":(exclude)src/crypto/sha256_x86_shani.cpp",
                 ]),
         )