Out-of-source build failed, AM_CXXFLAGS is not used

[Roman Rybalko <resiprocate@xxxxxxxxxxx>]

Hello reSIProcate devel people,

I'm trying to build resiprocate tree in another directory, i.e.
out-of-source build, and I see the following error:

libtool: compile:  g++ -DHAVE_CONFIG_H -I. -I../../resiprocate/repro -I.. 
-DRESIP_OSTYPE_LINUX -DRESIP_ARCH_X86_64 -DRESIP_LARCH_ -D_REENTRANT 
-DRESIP_TOOLCHAIN_GNU 
-DREPRO_DSO_PLUGIN_DIR_DEFAULT=\"/usr/local/lib/resiprocate/repro/plugins\" -g 
-Wall -Wno-deprecated -I/home/roma/work/resiprocate-build/rutil/dns/ares -MT 
librepro_la-AclStore.lo -MD -MP -MF .deps/librepro_la-AclStore.Tpo -c 
../../resiprocate/repro/AclStore.cxx  -fPIC -DPIC -o 
.libs/librepro_la-AclStore.o
../../resiprocate/repro/ConfigStore.cxx:2:28: fatal error: rutil/Logger.hxx: No 
such file or directory
 #include "rutil/Logger.hxx"
                            ^
compilation terminated.
../../resiprocate/repro/UserStore.cxx:3:31: fatal error: rutil/ResipAssert.h: 
No such file or directory
 #include "rutil/ResipAssert.h"
                               ^
compilation terminated.
../../resiprocate/repro/RouteStore.cxx:2:28: fatal error: rutil/Logger.hxx: No 
such file or directory
 #include "rutil/Logger.hxx"
                            ^
compilation terminated.
../../resiprocate/repro/StaticRegStore.cxx:2:28: fatal error: rutil/Logger.hxx: 
No such file or directory
 #include "rutil/Logger.hxx"
                            ^
compilation terminated.

I fixed this by changing AM_CXXFLAGS to AM_CPPFLAGS in all Makefile.am
files. The compile command then looks like this:

libtool: compile:  g++ -DHAVE_CONFIG_H -I. -I../../../resiprocate/resip/dum 
-I../.. -I ../../../resiprocate -DRESIP_OSTYPE_LINUX -DRESIP_ARCH_X86_64 
-DRESIP_LARCH_ -D_REENTRANT -DRESIP_TOOLCHAIN_GNU -g -Wall -Wno-deprecated 
-I/home/roma/work/resiprocate-build/rutil/dns/ares -MT ServerSubscription.lo 
-MD -MP -MF .deps/ServerSubscription.Tpo -c 
../../../resiprocate/resip/dum/ServerSubscription.cxx  -fPIC -DPIC -o 
.libs/ServerSubscription.o

i.e. -I ../../../resiprocate is added to the cmdline.

The page
gnu.org/software/automake/manual/html_node/Program-Variables.html
actually says that AM_CXXFLAGS is not supported.

Is there a particular reason for using AM_CXXFLAGS? If no, could you
please see my pull request?

-- 
Regards,
Roman