libsemanage/tests: include libsepol headers from $DESTDIR

When building and running tests on a system without SELinux with a
command similar to "make DESTDIR=/tmp/destdir install test", libsemanage
tests fail to build with the following error:

    In file included from utilities.h:20:0,
                     from utilities.c:24:
    ../src/handle.h:29:26: fatal error: sepol/handle.h: No such file or
    directory
     #include <sepol/handle.h>
                              ^

Fix this by adding the newly-installed directory under $DESTDIR (using
variable $PREFIX) in the search paths of the compiler.

Signed-off-by: Nicolas Iooss <nicolas.iooss@m4x.org>

.travis.yml

@@ -105,14 +105,12 @@ script:
   - make all -k
 
   # Set up environment variables for the tests
-  - export CFLAGS="-I$DESTDIR/usr/include"
   - export LD_LIBRARY_PATH="$DESTDIR/usr/lib:$DESTDIR/lib"
   - export PATH="$DESTDIR/usr/sbin:$DESTDIR/usr/bin:$DESTDIR/sbin:$DESTDIR/bin:$PATH"
   - export PYTHONPATH="$PYSITEDIR"
   - export RUBYLIB="$DESTDIR/$($RUBY -e 'puts RbConfig::CONFIG["vendorlibdir"]'):$DESTDIR/$($RUBY -e 'puts RbConfig::CONFIG["vendorarchdir"]')"
 
   # Show variables (to help debugging issues)
-  - echo "$CFLAGS"
   - echo "$LD_LIBRARY_PATH"
   - echo "$PATH"
   - echo "$PYTHONPATH"

libsemanage/tests/Makefile

@@ -11,7 +11,7 @@ LIBS = ../src/libsemanage.a -L$(LIBDIR) -lselinux -lsepol
 
 EXECUTABLE = libsemanage-tests
 CFLAGS += -g -O0 -Wall -W -Wundef -Wmissing-noreturn -Wmissing-format-attribute -Wno-unused-parameter
-INCLUDE = -I../src -I../include
+INCLUDE = -I../src -I../include -I$(PREFIX)/include
 LDFLAGS += -lcunit -lbz2 -laudit
 OBJECTS = $(SOURCES:.c=.o)