Remove PkgConfig dependence on Windows

PkgConfig works properly only on Linux. On Windows, it is part of the MSYS2 platform and there is no guarantee that it works properly; it is also not necessary.

Instead of using PkgConfig, a CMake module FindPkgVersionWin is introduced to find the version of a package from a config file.

find_pkg_version_win function is used to find the version of cerf package under Windows.

Related to issue #133 (closed)

cmake/commons/FindPkgVersion.cmake

@@ -38,6 +38,7 @@ function(find_pkg_version libname conffile paths output_var)
 
     string(STRIP "${paths}" _paths)
     string(STRIP "${conffile}" _pkgconffile)
+    set(_msghdr "find_pkg_version::")  # message header
 
     # find the configuration file in the given paths
     if(NOT _pkgconffile)
@@ -45,10 +46,9 @@ function(find_pkg_version libname conffile paths output_var)
     endif()
 
     # initialize the output variable
-    if(NOT output_var)
+    set(_outvar ${output_var})
+    if(NOT _outvar)
         set(_outvar ${libname}_VERSION)
-    else()
-        set(_outvar ${output_var})
     endif()
     set(${_outvar} "${_outvar}-NOTFOUND" PARENT_SCOPE)
 
@@ -59,13 +59,10 @@ function(find_pkg_version libname conffile paths output_var)
         PATHS "${_paths}" PATH_SUFFIXES "${_path_sfx}"
         DOC "Package configuration for ${_pkgconffile}")
 
-    # NOTE:
-    # A CMake value is False if the constant is 0, OFF, NO, FALSE,
-    # N, IGNORE, "", or ends in the suffix '-NOTFOUND'.
     if(${libname}_PATH)
-        message(STATUS "'${_pkgconffile}' found in '${${libname}_PATH}'")
+        message(STATUS "${_msghdr} '${_pkgconffile}' found in '${${libname}_PATH}'")
     else()
-        message(WARNING "'${_pkgconffile}' not found in paths {${_paths}}")
+        message(WARNING "${_msghdr} '${_pkgconffile}' not found in paths {${_paths}}")
         return()
     endif()
 
@@ -74,8 +71,11 @@ function(find_pkg_version libname conffile paths output_var)
     string(TOLOWER "${_conf}" _conf_lc)
     string(REGEX MATCH "version[: \t]*([1-9.]+)" _rxmatch ${_conf_lc})
 
-    if(${CMAKE_MATCH_1})
+    if(CMAKE_MATCH_1)
         set(${_outvar} "${CMAKE_MATCH_1}" PARENT_SCOPE)
+        message(STATUS "${_msghdr} ${_outvar} => ${CMAKE_MATCH_1}")
+    else()
+        message(WARNING "${_msghdr} ${_outvar} not found")
     endif ()
 
 endfunction()