Two small CMakeLists fixes (as discussed) (#1420)

* include (GNUInstallDirs) before using ${CMAKE_INSTALL_LIBDIR}

While here, trim some needless whitespace.

* Do not explicitly set APP_REVISION to an empty string

This allows to pass it on the command line when building from
GitHub-generated release tarballs which lack any Git metadata.

CMakeLists.txt

@@ -188,7 +188,7 @@ if(ENABLE_MEDIAPLAYER_LIBMPV)
   add_compile_definitions(ENABLE_MEDIAPLAYER_LIBMPV)
 endif()
 
-if(ENABLE_MEDIAPLAYER_QTMULTIMEDIA OR ENABLE_MEDIAPLAYER_LIBMPV)    
+if(ENABLE_MEDIAPLAYER_QTMULTIMEDIA OR ENABLE_MEDIAPLAYER_LIBMPV)
   set(ENABLE_MEDIAPLAYER TRUE)
   add_compile_definitions(ENABLE_MEDIAPLAYER)
 else()
@@ -245,8 +245,6 @@ if(REVISION_FROM_GIT AND EXISTS "${CMAKE_SOURCE_DIR}/.git")
   )
 
   message(STATUS "Detected git revision: '${APP_REVISION}'.")
-else()
-  set(APP_REVISION "")
 endif()
 
 if(NOT NO_LITE)

src/librssguard/CMakeLists.txt

@@ -371,7 +371,7 @@ set(UI_FILES
   services/abstract/gui/formfeeddetails.ui
 )
 
-if(ENABLE_MEDIAPLAYER) 
+if(ENABLE_MEDIAPLAYER)
   list(APPEND SOURCES
     gui/mediaplayer/playerbackend.cpp
     gui/mediaplayer/playerbackend.h
@@ -498,20 +498,12 @@ add_library(rssguard SHARED ${SOURCES} ${QM_FILES})
 if(FORCE_BUNDLE_ICONS)
   target_compile_definitions(rssguard
     PRIVATE
-
     FORCE_BUNDLE_ICONS
   )
 
   message(STATUS "Forcibly bundling icon themes.")
 endif()
 
-# Add specific definitions.
-target_compile_definitions(rssguard
-  PRIVATE
-  RSSGUARD_DLLSPEC=Q_DECL_EXPORT
-  RSSGUARD_LIBDIR="${CMAKE_INSTALL_LIBDIR}"
-)
-
 target_include_directories(rssguard
   PUBLIC
   ${CMAKE_CURRENT_SOURCE_DIR}
@@ -643,6 +635,13 @@ elseif(APPLE)
   set(HEADERS_FOLDER "Contents/Resources/Include")
 endif()
 
+# Add specific definitions.
+target_compile_definitions(rssguard
+  PRIVATE
+  RSSGUARD_DLLSPEC=Q_DECL_EXPORT
+  RSSGUARD_LIBDIR="${CMAKE_INSTALL_LIBDIR}"
+)
+
 # Install public headers.
 set(HEADERS_ROOT "${PROJECT_SOURCE_DIR}/src/librssguard")
 file(GLOB_RECURSE HEADER_FILES RELATIVE ${HEADERS_ROOT} "*.h")