gnu: clog: Add "-DUSE_SYSTEM_LIBS=ON" configure flag.

* gnu/packages/parallel.scm (clog)[arguments]: Add "-DUSE_SYSTEM_LIBS=ON"
to #:configure-flags.
* gnu/packages/patches/clog-fix-shared-build.patch: Adjust patch.

gnu/packages/parallel.scm

@@ -536,11 +536,14 @@ processor name, cache information, and topology information.")
               (inherit (package-source cpuinfo))
               (patches (search-patches "clog-fix-shared-build.patch"))))
     (arguments
-     (list #:configure-flags #~(list "-DBUILD_SHARED_LIBS=ON")
+     (list
-           #:phases #~(modify-phases %standard-phases
+      #:configure-flags
-                        (add-after 'unpack 'chdir
+      ''("-DBUILD_SHARED_LIBS=ON"
-                          (lambda _
+         "-DUSE_SYSTEM_LIBS=ON")
-                            (chdir "deps/clog"))))))
+      #:phases #~(modify-phases %standard-phases
+                   (add-after 'unpack 'chdir
+                     (lambda _
+                       (chdir "deps/clog"))))))
     (native-inputs (list googletest))
     (inputs '())
     (synopsis "C-style logging library based on printf")

gnu/packages/patches/clog-fix-shared-build.patch

@@ -1,50 +1,19 @@
 Author: Antero Mejr <antero@mailbox.org>
-Notes: Disabled function visibility hacks and googletest download. Enabled
+Notes: Disabled function visibility hacks. Enabled non-static builds.
-non-static builds.
 
 diff --git a/deps/clog/CMakeLists.txt b/deps/clog/CMakeLists.txt
-index 083f519..b7b225a 100644
+index 6e50c41..db02e95 100644
 --- a/deps/clog/CMakeLists.txt
 +++ b/deps/clog/CMakeLists.txt
-@@ -38,20 +38,8 @@ SET(CONFU_DEPENDENCIES_SOURCE_DIR ${CMAKE_SOURCE_DIR}/deps
+@@ -55,7 +55,7 @@ IF(CLOG_BUILD_TESTS)
- SET(CONFU_DEPENDENCIES_BINARY_DIR ${CMAKE_BINARY_DIR}/deps
+ ENDIF()
-   CACHE PATH "Confu-style dependencies binary directory")
  
--IF(CLOG_BUILD_TESTS)
--  IF(NOT DEFINED GOOGLETEST_SOURCE_DIR)
--    MESSAGE(STATUS "Downloading Google Test to ${CONFU_DEPENDENCIES_SOURCE_DIR}/googletest (define GOOGLETEST_SOURCE_DIR to avoid it)")
--    CONFIGURE_FILE(cmake/DownloadGoogleTest.cmake "${CONFU_DEPENDENCIES_BINARY_DIR}/googletest-download/CMakeLists.txt")
--    EXECUTE_PROCESS(COMMAND "${CMAKE_COMMAND}" -G "${CMAKE_GENERATOR}" .
--      WORKING_DIRECTORY "${CONFU_DEPENDENCIES_BINARY_DIR}/googletest-download")
--    EXECUTE_PROCESS(COMMAND "${CMAKE_COMMAND}" --build .
--      WORKING_DIRECTORY "${CONFU_DEPENDENCIES_BINARY_DIR}/googletest-download")
--    SET(GOOGLETEST_SOURCE_DIR "${CONFU_DEPENDENCIES_SOURCE_DIR}/googletest" CACHE STRING "Google Test source directory")
--  ENDIF()
--ENDIF()
--
  # ---[ clog library
 -ADD_LIBRARY(clog STATIC src/clog.c)
 +ADD_LIBRARY(clog src/clog.c)
  SET_TARGET_PROPERTIES(clog PROPERTIES
    C_STANDARD 99
    C_EXTENSIONS NO)
-@@ -74,16 +62,6 @@ INSTALL(TARGETS clog
- 
- # ---[ clog tests
- IF(CLOG_BUILD_TESTS)
--  # ---[ Build google test
--  IF(NOT TARGET gtest)
--    IF(MSVC AND NOT CLOG_RUNTIME_TYPE STREQUAL "static")
--      SET(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
--    ENDIF()
--    ADD_SUBDIRECTORY(
--      "${GOOGLETEST_SOURCE_DIR}"
--      "${CONFU_DEPENDENCIES_BINARY_DIR}/googletest")
--  ENDIF()
--
-   ADD_EXECUTABLE(clog-test test/clog.cc)
-   SET_TARGET_PROPERTIES(clog-test PROPERTIES
-     CXX_STANDARD 11
 diff --git a/deps/clog/include/clog.h b/deps/clog/include/clog.h
 index 4143761..aa9000f 100644
 --- a/deps/clog/include/clog.h