cmake: verify minimum libcm256cc version via pkg-config

libcm256cc does not expose its package version through its headers or
shared library, making it impossible to verify a minimum supported
version after discovery leading to errors when building.

When CM256CC_DIR is not specified, use pkg-config to verify that
libcm256cc >= 1.1.2 is available before searching for the headers and
library. If the required version is not found, disable CM256 support
and continue configuring the rest of the project.

When CM256CC_DIR is provided, treat it as an explicit user override and
search that installation directly and blindly (don't check version).

Also update the pkg-config hint variables to use the documented
*_INCLUDE_DIRS and *_LIBRARY_DIRS outputs from pkg_check_modules().
https://cmake.org/cmake/help/latest/module/FindPkgConfig.html

Signed-off-by: Robin Getz <rgetz503@gmail.com>

cmake/Modules/FindCM256cc.cmake

@@ -1,11 +1,29 @@
+# If CM256CC_DIR is specified, treat it as an explicit user override and
+# search that installation directly. Otherwise, use pkg-config to verify
+# the minimum supported libcm256cc version, since the library itself does
+# not expose version information through its headers or shared library.
+
 if (NOT CM256CC_FOUND)
-    INCLUDE(FindPkgConfig)
-    PKG_CHECK_MODULES(PC_CM256cc "libcm256cc")
+    if(CM256CC_DIR)
+        message(STATUS "Using CM256CC_DIR: ${CM256CC_DIR}")
+    else()
+        find_package(PkgConfig QUIET)
+        if(NOT PKG_CONFIG_FOUND)
+            message(STATUS "CM256CC support disabled: pkg-config is required to verify libcm256cc.")
+            return()
+        endif()
+
+        pkg_check_modules(PC_CM256CC QUIET libcm256cc>=1.1.2)
+        if(NOT PC_CM256CC_FOUND)
+            message(STATUS "CM256CC support disabled: libcm256cc >= 1.1.2 was not found.")
+            return()
+        endif()
+    endif()
 
     FIND_PATH(CM256CC_INCLUDE_DIR
         NAMES cm256cc/cm256.h
         HINTS ${CM256CC_DIR}/include
-              ${PC_CM256CC_INCLUDE_DIR}
+              ${PC_CM256CC_INCLUDE_DIRS}
               ${CMAKE_INSTALL_PREFIX}/include
         PATHS /usr/local/include
               /usr/include
@@ -15,7 +33,7 @@ if (NOT CM256CC_FOUND)
         NAMES cm256cc libcm256cc
         HINTS ${CM256CC_DIR}/lib
               ${CM256CC_DIR}/lib64
-              ${PC_CM256CC_LIBDIR}
+              ${PC_CM256CC_LIBRARY_DIRS}
               ${CMAKE_INSTALL_PREFIX}/lib
               ${CMAKE_INSTALL_PREFIX}/lib64
         PATHS /usr/local/lib