MDEV-34787: invalid instruction signal 4

Changes for powerpc in git commit dec3f8ca assume power8 VSX
extensions for faster crc32 support, but earlier processors
(e.g. power5) don't have them.  On unexpected powerpc chips,
we will not use an optimized crc32 implementation.  CMake does
not provide a facility to detect processor features or in the
case of powerpc, flavors of the chip.  Create a place where we
can detect such flavors and caveat as necessary.

mysys/CMakeLists.txt

@@ -134,7 +134,10 @@ ELSEIF(CMAKE_SYSTEM_PROCESSOR MATCHES "aarch64|AARCH64")
   ENDIF()
 ENDIF()
 
-IF(CMAKE_SYSTEM_PROCESSOR MATCHES "ppc64|powerpc64" OR CMAKE_SYSTEM_NAME MATCHES AIX)
+cmake_host_system_information(RESULT procname QUERY PROCESSOR_NAME)
+string(FIND ${procname} "PPC970" proc_is_ppc970)
+IF((proc_is_ppc970 EQUAL -1) AND
+   (CMAKE_SYSTEM_PROCESSOR MATCHES "ppc64|powerpc64" OR CMAKE_SYSTEM_NAME MATCHES AIX))
   SET(MYSYS_SOURCES ${MYSYS_SOURCES} crc32/crc32_ppc64.c crc32/crc32c_ppc.c)
   SET_SOURCE_FILES_PROPERTIES(crc32/crc32_ppc64.c crc32/crc32c_ppc.c PROPERTIES
         COMPILE_FLAGS "${COMPILE_FLAGS} -maltivec -mvsx -mpower8-vector -mcrypto -mpower8-vector")

mysys/crc32ieee.cc

@@ -50,9 +50,6 @@ static my_crc32_t init_crc32()
 
 static const my_crc32_t my_checksum_func= init_crc32();
 
-#ifdef __powerpc64__
-# error "my_checksum() is defined in mysys/crc32/crc32_ppc64.c"
-#endif
 extern "C"
 unsigned int my_checksum(unsigned int crc, const void *data, size_t len)
 {