CMake Powershell tests

Some CMake tests need to use shell redirection to input file content. This is often done on Unix-like systems by invoking sh -c. Powershell can also work (including on Windows) if proper escaping is used:

find_program(PWSH NAMES pwsh powershell)

if(PWSH)
  add_test(NAME test1
    COMMAND ${PWSH} -c \"Get-Content ${CMAKE_CURRENT_SOURCE_DIR}/myfile.txt | $<TARGET_FILE:myexe>\")
elseif(UNIX)
  add_test(NAME test1
    COMMAND sh -c "$<TARGET_FILE:myexe> < ${CMAKE_CURRENT_SOURCE_DIR}/myfile.txt")
endif()

# arbitrary example
if(TEST test1)
  set_tests_properties(test1 PROPERTIES TIMEOUT 10)
endif()