replace configure's ARCH... with Q_PROCESSOR_... v2

[ulmus-scott]

Was in #470

Separated from other changes.

HAVE_INTRINSICS_NEON

mythtv/mythtv/configure

Line 5568 in 8cbe838

check_code cc arm_neon.h "int16x8_t test = vdupq_n_s16(0)" && enable intrinsics_neon

[linuxdude42]

Commit 93de0f8 with the HAVE_INTRINSICS_NEON change is causing build failures on an rpi3. I'm seeing the following errors:

In file included from mythdeinterlacer.cpp:25:
/usr/lib/gcc/arm-linux-gnueabihf/10/include/arm_neon.h: In function ‘void BlendSIMD8x4(unsigned char*, int, int, int, int, unsigned char*, int, bool)’:
/usr/lib/gcc/arm-linux-gnueabihf/10/include/arm_neon.h:903:1: error: inlining failed in call to ‘always_inline’ ‘uint16x8_t vrhaddq_u16(uint16x8_t, uint16x8_t)’: target specific option mismatch
  903 | vrhaddq_u16 (uint16x8_t __a, uint16x8_t __b)
      | ^~~~~~~~~~~
mythdeinterlacer.cpp:617:32: note: called from here
  617 |                     vrhaddq_u16(*reinterpret_cast<uint16x8_t*>(&below[col]), mid);
      |                     ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from mythdeinterlacer.cpp:25:
/usr/lib/gcc/arm-linux-gnueabihf/10/include/arm_neon.h:903:1: error: inlining failed in call to ‘always_inline’ ‘uint16x8_t vrhaddq_u16(uint16x8_t, uint16x8_t)’: target specific option mismatch
  903 | vrhaddq_u16 (uint16x8_t __a, uint16x8_t __b)
      | ^~~~~~~~~~~
mythdeinterlacer.cpp:615:32: note: called from here
  615 |                     vrhaddq_u16(*reinterpret_cast<uint16x8_t*>(&above[col]), mid);
      |                     ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
make[2]: *** [Makefile:18542: obj/mythdeinterlacer.o] Error 1

This change doesn't have the additional compilation test that configure does on line 5568, which is apparently necessary.

[garybuhrmaster]

Commit 93de0f8 with the HAVE_INTRINSICS_NEON change is causing build failures on an rpi3.

And was first reported failed by the armv7 buildbot worker on irc on 2022-02-18.

[ulmus-scott]

The builder @garybuhrmaster referenced uses -march=armv7-a.

GCC may want -march=armv7-a+simd or -mfpu=neon. It won't auto-vectorize NEON, so should be safe.
https://gcc.gnu.org/onlinedocs/gcc/ARM-Options.html#ARM-Options

The used intrinsic is valid: https://developer.arm.com/architectures/instruction-sets/intrinsics/#q=vrhaddq_u16