libcamera: Fix base and ipa include dir

All libcamera headers are meant to be installed in
${prefix}/include/libcamera/libcamera, with pkgconfig specifying the
include directory as `-I ${prefix}/include/libcamera`. Applications then
include the headers with `#include <libcamera/camera.h>`.

The base and ipa headers are meant to be installed in subdirectories of
the libcamera headers directory, but are mistakenly installed one level
too high, in ${prefix}/include/libcamera. This leads to compilation
failures when including the base or ipa header.

Fix this by setting the meson libcamera_include_dir variable to the
libcamera headers directory. All other header paths are derived from
that variable and are now correct.

Reported-by: Dorota Czaplejewicz <dorota.czaplejewicz@puri.sm>
Bug: https://bugs.libcamera.org/show_bug.cgi?id=79
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

include/meson.build

@@ -1,6 +1,4 @@
 # SPDX-License-Identifier: CC0-1.0
 
-libcamera_include_dir = 'libcamera'
-
 subdir('android')
 subdir('libcamera')