Revert "Use system gflags only in samples (#18478)" (#18543)

This reverts commit bca3f3e441.

thirdparty/dependencies.cmake

@@ -4,6 +4,8 @@
 
 if(CMAKE_TOOLCHAIN_FILE MATCHES "vcpkg" OR DEFINED VCPKG_VERBOSE)
     set(OV_VCPKG_BUILD ON)
+elseif(CMAKE_TOOLCHAIN_FILE MATCHES "conan_toolchain" OR DEFINED CONAN_EXPORTED)
+    set(OV_CONAN_BUILD)
 endif()
 
 set(_old_CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS})
@@ -367,8 +369,51 @@ endif()
 #
 
 if(ENABLE_SAMPLES OR ENABLE_TESTS)
-    add_subdirectory(thirdparty/gflags EXCLUDE_FROM_ALL)
-    openvino_developer_export_targets(COMPONENT openvino_common TARGETS gflags)
+    if(OV_VCPKG_BUILD OR OV_CONAN_BUILD)
+        # vcpkg contains only libs compiled with threads
+        # conan case
+        find_package(gflags QUIET)
+    elseif(APPLE OR WIN32)
+        # on Windows and macOS we don't use gflags, because will be dynamically linked
+    elseif(CMAKE_HOST_LINUX AND LINUX)
+        if(OV_OS_RHEL)
+            set(gflag_component nothreads_shared)
+        elseif(OV_OS_DEBIAN)
+            set(gflag_component nothreads_static)
+        endif()
+        find_package(gflags QUIET OPTIONAL_COMPONENTS ${gflag_component})
+    endif()
+
+    if(gflags_FOUND)
+        if(TARGET gflags)
+            # no extra steps
+        elseif(TARGET gflags_nothreads-static)
+            # Debian 9: gflag_component is ignored
+            set(gflags_target gflags_nothreads-static)
+        elseif(TARGET gflags_nothreads-shared)
+            # CentOS / RHEL / Fedora case
+            set(gflags_target gflags_nothreads-shared)
+        elseif(TARGET ${GFLAGS_TARGET})
+            set(gflags_target ${GFLAGS_TARGET})
+        else()
+            message(FATAL_ERROR "Internal error: failed to find imported target 'gflags' using '${gflag_component}' component")
+        endif()
+
+        if(gflags_target)
+            if(OV_PkgConfig_VISILITY)
+                # need to set GLOBAL visibility in order to create ALIAS for this target
+                set_target_properties(${gflags_target} PROPERTIES IMPORTED_GLOBAL ON)
+            endif()
+            add_library(gflags ALIAS ${gflags_target})
+        endif()
+
+        message(STATUS "gflags (${gflags_VERSION}) is found at ${gflags_DIR} using '${gflag_component}' component")
+    endif()
+
+    if(NOT TARGET gflags)
+        add_subdirectory(thirdparty/gflags EXCLUDE_FROM_ALL)
+        openvino_developer_export_targets(COMPONENT openvino_common TARGETS gflags)
+    endif()
 endif()
 
 #
@@ -590,6 +635,9 @@ endif()
 if(CPACK_GENERATOR MATCHES "^(DEB|RPM|CONDA-FORGE|BREW|CONAN|VCPKG)$")
     # These libraries are dependencies for openvino-samples package
     if(ENABLE_SAMPLES OR ENABLE_TESTS)
+        if(NOT gflags_FOUND AND CPACK_GENERATOR MATCHES "^(DEB|RPM)$")
+            message(FATAL_ERROR "gflags must be used as a ${CPACK_GENERATOR} package. Install libgflags-dev / gflags-devel")
+        endif()
         if(NOT (zlib_FOUND OR ZLIB_FOUND))
             message(FATAL_ERROR "zlib must be used as a ${CPACK_GENERATOR} package. Install zlib1g-dev / zlib-devel")
         endif()