Avoid semicolon insertion when modifying linker flags

Jenkinsfile

@@ -62,9 +62,8 @@ pipeline{
             [os: 'fedora', ver: '32',    arch: 'x86_64', compiler: 'gcc-10'],
             [os: 'fedora', ver: '33',    arch: 'x86_64', compiler: 'gcc-10'],
             [os: 'fedora', ver: '34',    arch: 'x86_64', compiler: 'gcc-11'],
-            [os: 'macos',  ver: '13',    arch: 'x86_64', compiler: 'apple-clang-15'],
-            [os: 'macos',  ver: '14',    arch: 'x86_64', compiler: 'apple-clang-15'],
-            [os: 'macos',  ver: '14',    arch: 'arm64',  compiler: 'apple-clang-15'],
+            [os: 'macos',  ver: '12',    arch: 'x86_64', compiler: 'apple-clang-13'],
+            [os: 'macos',  ver: '12',    arch: 'arm64',  compiler: 'apple-clang-13'],
           ])
 
           parallel(builds)

cmake/FairLoggerLib.cmake

@@ -128,8 +128,8 @@ macro(set_fairlogger_defaults)
   list(FIND CMAKE_PLATFORM_IMPLICIT_LINK_DIRECTORIES "${CMAKE_INSTALL_PREFIX}/${PROJECT_INSTALL_LIBDIR}" isSystemDir)
   if("${isSystemDir}" STREQUAL "-1")
     if(CMAKE_SYSTEM_NAME STREQUAL "Linux")
-      list(APPEND CMAKE_EXE_LINKER_FLAGS "-Wl,--enable-new-dtags")
-      list(APPEND CMAKE_SHARED_LINKER_FLAGS "-Wl,--enable-new-dtags")
+      string(APPEND CMAKE_EXE_LINKER_FLAGS " -Wl,--enable-new-dtags")
+      string(APPEND CMAKE_SHARED_LINKER_FLAGS " -Wl,--enable-new-dtags")
       list(APPEND CMAKE_INSTALL_RPATH "$ORIGIN/../${PROJECT_INSTALL_LIBDIR}")
     elseif(CMAKE_SYSTEM_NAME STREQUAL "Darwin")
       list(APPEND CMAKE_INSTALL_RPATH "@loader_path/../${PROJECT_INSTALL_LIBDIR}")