Use explicit no-sse flags when SSE is off

Also:
- Silence clang warnings about unsupported command line arguments
- Add diagnostic print to calib3d test
- Fixed perf test relative error check
- Fix iOS build problem

cmake/OpenCVCompilerOptions.cmake

@@ -98,6 +98,10 @@ if(CMAKE_COMPILER_IS_GNUCXX)
     add_extra_compiler_option(-pthread)
   endif()
 
+  if(CMAKE_COMPILER_IS_CLANGCXX)
+    add_extra_compiler_option(-Qunused-arguments)
+  endif()
+
   if(OPENCV_WARNINGS_ARE_ERRORS)
     add_extra_compiler_option(-Werror)
   endif()
@@ -127,6 +131,8 @@ if(CMAKE_COMPILER_IS_GNUCXX)
   endif()
   if(ENABLE_SSE2)
     add_extra_compiler_option(-msse2)
+  elseif(X86 OR X86_64)
+    add_extra_compiler_option(-mno-sse2)
   endif()
   if(ENABLE_NEON)
     add_extra_compiler_option("-mfpu=neon")
@@ -139,6 +145,8 @@ if(CMAKE_COMPILER_IS_GNUCXX)
   if(NOT MINGW)
     if(ENABLE_AVX)
       add_extra_compiler_option(-mavx)
+    elseif(X86 OR X86_64)
+      add_extra_compiler_option(-mno-avx)
     endif()
     if(ENABLE_AVX2)
       add_extra_compiler_option(-mavx2)
@@ -152,18 +160,26 @@ if(CMAKE_COMPILER_IS_GNUCXX)
     if(NOT OPENCV_EXTRA_CXX_FLAGS MATCHES "-mavx")
       if(ENABLE_SSE3)
         add_extra_compiler_option(-msse3)
+      elseif(X86 OR X86_64)
+        add_extra_compiler_option(-mno-sse3)
       endif()
 
       if(ENABLE_SSSE3)
         add_extra_compiler_option(-mssse3)
+      elseif(X86 OR X86_64)
+        add_extra_compiler_option(-mno-ssse3)
       endif()
 
       if(ENABLE_SSE41)
         add_extra_compiler_option(-msse4.1)
+      elseif(X86 OR X86_64)
+        add_extra_compiler_option(-mno-sse4.1)
       endif()
 
       if(ENABLE_SSE42)
         add_extra_compiler_option(-msse4.2)
+      elseif(X86 OR X86_64)
+        add_extra_compiler_option(-mno-sse4.2)
       endif()
 
       if(ENABLE_POPCNT)