Merge #57: cmake: Backport changes from master

02392e7 fixup! cmake: Build `crc32c` static library (Hennadii Stepanov)
a682425 fixup! cmake: Check system symbols (Hennadii Stepanov)

Pull request description:

  The first commit fixes a regression, which makes tests running with the empty `CMAKE_REQUIRED_FLAGS` variable. It was introduced during updating the code for the minimum CMake 3.16.

  The second commit mirrors bitcoin#28919.

ACKs for top commit:
  pablomartin4btc:
    tACK 02392e7

Tree-SHA512: 80a8fb13367b3b5be7db2663dc82667400b527c49ea22b4c07abcc916797e0cdbc1348d28bbd02e7b7f4c34f5e7d816947517d3998449e5fa963ba84f8a0690d

cmake/crc32c.cmake

@@ -61,7 +61,7 @@ check_cxx_source_compiles_with_flags("${SSE42_CXXFLAGS}" "
 )
 
 # Check for ARMv8 w/ CRC and CRYPTO extensions support in the compiler.
-set(ARM_CRC_CXXFLAGS -march=armv8-a+crc)
+set(ARM_CRC_CXXFLAGS -march=armv8-a+crc+crypto)
 check_cxx_source_compiles_with_flags("${ARM_CRC_CXXFLAGS}" "
   #include <arm_acle.h>
   #include <arm_neon.h>

cmake/module/CheckSourceCompilesAndLinks.cmake

@@ -16,14 +16,16 @@ endmacro()
 
 macro(check_cxx_source_compiles_with_flags flags source)
   cmake_push_check_state(RESET)
-  list(JOIN flags " " CMAKE_REQUIRED_FLAGS)
+  set(CMAKE_REQUIRED_FLAGS ${flags})
+  list(JOIN CMAKE_REQUIRED_FLAGS " " CMAKE_REQUIRED_FLAGS)
   check_cxx_source_compiles("${source}" ${ARGN})
   cmake_pop_check_state()
 endmacro()
 
 macro(check_cxx_source_links_with_flags flags source)
   cmake_push_check_state(RESET)
-  list(JOIN flags " " CMAKE_REQUIRED_FLAGS)
+  set(CMAKE_REQUIRED_FLAGS ${flags})
+  list(JOIN CMAKE_REQUIRED_FLAGS " " CMAKE_REQUIRED_FLAGS)
   check_cxx_source_links("${source}" ${ARGN})
   cmake_pop_check_state()
 endmacro()