CMake: Remove glibc version detection

If we were conditionally enabling _BSD_SOURCE or _SVID_SOURCE, I can
understand trying to play nice with the compiler and only pass as
needed, however this is not the case and glibc <= 2.19 will not care
that we are passing _DEFAULT_SOURCE. This removes an unnecessary
build step and gives us less to maintain from a build system
perspective.

Small cosmetic changes to MacroQbtCompilerSettings are included.

cmake/Modules/MacroGlibcDetect.cmake

@@ -1,49 +0,0 @@
- ###############################################################
- #
- # Copyright 2011 Red Hat, Inc.
- #
- # Licensed under the Apache License, Version 2.0 (the "License"); you
- # may not use this file except in compliance with the License.  You may
- # obtain a copy of the License at
- #
- #    http://www.apache.org/licenses/LICENSE-2.0
- #
- # Unless required by applicable law or agreed to in writing, software
- # distributed under the License is distributed on an "AS IS" BASIS,
- # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- # See the License for the specific language governing permissions and
- # limitations under the License.
- #
- ###############################################################
-
-MACRO (GLIBC_DETECT _VERSION)
-
-# there are multiple ways to detect glibc, but given nmi's
-# cons'd up paths I will trust only gcc.  I guess I could also use
-# ldd --version to detect.
-
-    set(_GLIB_SOURCE_DETECT "
-#include <limits.h>
-#include <stdio.h>
-int main()
-{
-  printf(\"%d%d\",__GLIBC__, __GLIBC_MINOR__);
-  return 0;
-}
-")
-
-file (WRITE ${CMAKE_CURRENT_BINARY_DIR}/build/cmake/glibc.cpp "${_GLIB_SOURCE_DETECT}\n")
-
-try_run(POST26_GLIBC_DETECTED
-        POST26_GLIBC_COMPILE
-        ${CMAKE_CURRENT_BINARY_DIR}/build/cmake
-        ${CMAKE_CURRENT_BINARY_DIR}/build/cmake/glibc.cpp
-        RUN_OUTPUT_VARIABLE GLIBC_VERSION )
-
-if (GLIBC_VERSION AND POST26_GLIBC_COMPILE )
-    set(${_VERSION} ${GLIBC_VERSION})
-else()
-    message(STATUS "NOTE: Could not detect GLIBC_VERSION from compiler")
-endif()
-
-ENDMACRO (GLIBC_DETECT)

cmake/Modules/MacroQbtCompilerSettings.cmake

@@ -24,8 +24,8 @@ macro(qbt_set_compiler_options)
             #"-Wno-error=sign-conversion -Wno-error=float-equal"
         )
 
+        # GCC 4.8 has problems with std::array and its initialization
         if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU" AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.9)
-            # GCC 4.8 has problems with std::array and its initialization
             list(APPEND _GCC_COMMON_CXX_FLAGS "-Wno-error=missing-field-initializers")
         endif()
 
@@ -39,22 +39,11 @@ macro(qbt_set_compiler_options)
         endif (_PEDANTIC_IS_SUPPORTED)
 
         if (CMAKE_SYSTEM_NAME MATCHES Linux)
-            # if Glibc version is 2.20 or higher, set -D_DEFAULT_SOURCE
-            include(MacroGlibcDetect)
-            message(STATUS "Detecting Glibc version...")
-            glibc_detect(GLIBC_VERSION)
-            if(${GLIBC_VERSION})
-                if(GLIBC_VERSION LESS "220")
-                    message(STATUS "Glibc version is ${GLIBC_VERSION}")
-                else(GLIBC_VERSION LESS "220")
-                    message(STATUS "Glibc version is ${GLIBC_VERSION}, adding -D_DEFAULT_SOURCE")
-                    add_definitions(-D_DEFAULT_SOURCE)
-                endif(GLIBC_VERSION LESS "220")
-            endif(${GLIBC_VERSION})
-        endif (CMAKE_SYSTEM_NAME MATCHES Linux)
+            add_definitions(-D_DEFAULT_SOURCE)
+        endif()
 
+        # Clang 5.0 still doesn't support -Wstrict-null-sentinel
         if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
-            # Clang 5.0 still doesn't support -Wstrict-null-sentinel
             check_cxx_compiler_flag(-Wstrict-null-sentinel _STRICT_NULL_SENTINEL_IS_SUPPORTED)
             if (_STRICT_NULL_SENTINEL_IS_SUPPORTED)
                 list(APPEND _GCC_COMMON_CXX_FLAGS "-Wstrict-null-sentinel")
@@ -75,7 +64,7 @@ macro(qbt_set_compiler_options)
     endif ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU" OR "${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
 
     if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "MSVC")
-        set(QBT_ADDITONAL_FLAGS "-wd4290 -wd4275 -wd4251 /W4" CACHE STRING "Additional qBittorent compile flags")
+        set(QBT_ADDITONAL_FLAGS "/wd4251 /wd4275 /wd4290  /W4" CACHE STRING "Additional qBittorent compile flags")
     endif ()
 
     string(APPEND CMAKE_C_FLAGS " ${QBT_ADDITONAL_FLAGS}")