builds should look in the build tree for header files first

In the course of building libvmdk-20210418 while libvmdk-20200926 was already installed, I encountered the following error due to the build including the installed /usr/local/include/libvmdk/definitions.h:

--- pyvmdk_la-pyvmdk_disk_types.lo ---
libtool: compile:  cc -DHAVE_CONFIG_H -I. -I../common -I/usr/local/include/python3.8 -I/usr/local/include/py
thon3.8 -I/usr/local/include -I../include -I../common -I../libcerror -I../libcdata -I../libclocale -I../libc
split -I../libuna -I../libcfile -I../libcpath -I../libbfio -O2 -pipe -fstack-protector-strong -fno-strict-al
iasing -Wall -MT pyvmdk_la-pyvmdk_disk_types.lo -MD -MP -MF .deps/pyvmdk_la-pyvmdk_disk_types.Tpo -c pyvmdk_
disk_types.c  -fPIC -DPIC -o .libs/pyvmdk_la-pyvmdk_disk_types.o
pyvmdk_disk_types.c:149:18: error: use of undeclared identifier 'LIBVMDK_DISK_TYPE_FLAT_2GB_EXTENT'; did you
 mean 'LIBVMDK_DISK_TYPE_2GB_EXTENT_FLAT'?
                        LIBVMDK_DISK_TYPE_FLAT_2GB_EXTENT );
                        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                        LIBVMDK_DISK_TYPE_2GB_EXTENT_FLAT
/usr/local/include/libvmdk/definitions.h:68:2: note: 'LIBVMDK_DISK_TYPE_2GB_EXTENT_FLAT' declared here
        LIBVMDK_DISK_TYPE_2GB_EXTENT_FLAT,
        ^
pyvmdk_disk_types.c:163:18: error: use of undeclared identifier 'LIBVMDK_DISK_TYPE_SPARSE_2GB_EXTENT'; did y
ou mean 'LIBVMDK_DISK_TYPE_2GB_EXTENT_FLAT'?
                        LIBVMDK_DISK_TYPE_SPARSE_2GB_EXTENT );
                        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                        LIBVMDK_DISK_TYPE_2GB_EXTENT_FLAT
/usr/local/include/libvmdk/definitions.h:68:2: note: 'LIBVMDK_DISK_TYPE_2GB_EXTENT_FLAT' declared here
        LIBVMDK_DISK_TYPE_2GB_EXTENT_FLAT,
        ^
2 errors generated.
*** [pyvmdk_la-pyvmdk_disk_types.lo] Error code 1

The arguments for the configure stage were:

  $ ./configure --enable-python --with-libintl-prefix=/usr/local --prefix=/usr/local --localstatedir=/var --mandir=/usr/local/man --disable-silent-rules --infodir=/usr/local/share/info/ --build=amd64-portbld-freebsd11.4

The -I/usr/local/include comes from CPPFLAGS. The relevant build target in pyvmdk/Makefile is:

pyvmdk_la-pyvmdk_disk_types.lo: pyvmdk_disk_types.c
        $(AM_V_CC)$(LIBTOOL) $(AM_V_lt) --tag=CC $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=compile $(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(pyvmdk_la_CPPFLAGS) $(CPPFLAGS) $(AM_CFLAGS) $(CFLAGS) -MT pyvmdk_la-pyvmdk_disk_types.lo -MD -MP -MF $(DEPDIR)/pyvmdk_la-pyvmdk_disk_types.Tpo -c -o pyvmdk_la-pyvmdk_disk_types.lo `test -f 'pyvmdk_disk_types.c' || echo '$(srcdir)/'`pyvmdk_disk_types.c
        $(AM_V_at)$(am__mv) $(DEPDIR)/pyvmdk_la-pyvmdk_disk_types.Tpo $(DEPDIR)/pyvmdk_la-pyvmdk_disk_types.Plo

Currently pyvmdk/Makefile.am defines AM_CFLAGS which comes after CPPFLAGS in the compile command.

libyal / libvmdk

builds should look in the build tree for header files first #27