Guard CPU_ProbeARMv7 with CRYPTOPP_BOOL_ARM32 (GH #844)

We make these queries available on all platforms so folks don't need to guard code.

neon_simd.cpp

@@ -51,7 +51,8 @@ bool CPU_ProbeARMv7()
 {
 #if defined(CRYPTOPP_NO_CPU_FEATURE_PROBES)
 	return false;
-#elif defined(CRYPTOPP_MS_STYLE_INLINE_ASSEMBLY)
+#elif CRYPTOPP_BOOL_ARM32
+# if defined(CRYPTOPP_MS_STYLE_INLINE_ASSEMBLY)
 	volatile bool result = true;
 	__try
 	{
@@ -115,6 +116,8 @@ bool CPU_ProbeARMv7()
 	return result;
 # else
 	return false;
+# endif
+	return false;
 #endif  // CRYPTOPP_ARM_NEON_AVAILABLE
 }