build: use GNUInstallDirs where possible

Some installation destinations were already converted to the
GNUInstallDirs standard in e3cf4d0cf. This patch converts the share and
include directories (typically /usr/share and /usr/include respectively)
as well.

Type: improvement
Change-Id: Id481b16604f3f52203166a5c0647f43d6eb05239
Signed-off-by: Wim de With <wf@dewith.io>
diff --git a/src/tools/vppapigen/CMakeLists.txt b/src/tools/vppapigen/CMakeLists.txt
index 04ebed5..97a6d35 100644
--- a/src/tools/vppapigen/CMakeLists.txt
+++ b/src/tools/vppapigen/CMakeLists.txt
@@ -43,7 +43,7 @@
     vppapigen_json.py
     generate_json.py
   DESTINATION
-    share/vpp
+    ${CMAKE_INSTALL_DATADIR}/vpp
   COMPONENT
     vpp-dev
 )