capnproto: remove binaries from target-build, add bbclass

When linking to capnproto from another project, cmake fails to
find this package with the following error:

| CMake Error at ${RECIPE_SYSROOT}/usr/lib/cmake/CapnProto/CapnProtoTargets.cmake:176 (message):
|   The imported target "CapnProto::capnp_tool" references the file
|
|      "${RECIPE_SYSROOT}/usr/bin/capnp"
|
|   but this file does not exist.  Possible reasons include:

To solve this, this change includes the following:

1. Add a patch that removes the files installed (and exported) in
${bindir} from the target build. The CMake file originally verified
that these files exist when another recipe tried to use it, however
the ${RECIPE_SYSROOT} does not contain the binaries in ${bindir},
so it failed quick in the do_configure step. (This alone is enough
to link against the cross-compiled libraries of capnproto successfully,
but code-generation from capnproto definition fails)

2. Add a new bbclass for capnproto. To cross-compile an application
that uses capnproto, the application needs to be linked against the
cross-compiled version of the libraries, however the native version
of the binaries need to be used to generate C++ code from the
capnproto definitions. This class sets the correct CMake arguments, to
use the capnproto binaries from the native package, instead of looking
for the non-existent cross-compiled binaries. (These variables can
be found in ${libdir}/cmake/CapnProto/CapnProtoConfig.cmake file)

Signed-off-by: Gyorgy Sarvari <skandigraun@gmail.com>
Signed-off-by: Khem Raj <raj.khem@gmail.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/meta-oe/classes/capnproto.bbclass b/meta-oe/classes/capnproto.bbclass
new file mode 100644
index 0000000000..a698f41c95
--- /dev/null
+++ b/meta-oe/classes/capnproto.bbclass
@@ -0,0 +1,8 @@
+# Inherit this class in your recipe to compile against 
+# Cap'N Proto (capnproto) with CMake
+
+DEPENDS:append = " capnproto-native "
+DEPENDS:append:class-target = " capnproto "
+
+EXTRA_OECMAKE:append:class-target = " -DCAPNP_EXECUTABLE=${RECIPE_SYSROOT_NATIVE}${bindir}/capnp \
+                                      -DCAPNPC_CXX_EXECUTABLE=${RECIPE_SYSROOT_NATIVE}${bindir}/capnpc-c++ "