[cross-compiling] Disable document generation during cross-compilation

Document generation requires exec'ing lnav which might not be possible
while cross-compiling.

configure.ac

@@ -277,6 +277,7 @@ AS_IF([test $? -eq 0],
 
 AM_CONDITIONAL(USE_INCLUDED_YAJL, test $HAVE_LOCAL_YAJL -eq 0)
 AM_CONDITIONAL(HAVE_LIBCURL, test x"$LIBCURL" != x"")
+AM_CONDITIONAL([DISABLE_DOCUMENTATION], [ test x"$cross_compiling" != x"no" ])
 
 AC_CONFIG_HEADERS([src/config.h])
 AC_CONFIG_FILES([Makefile])

src/Makefile.am

@@ -483,8 +483,10 @@ uncrusty:
 	(cd $(srcdir) && uncrustify -c ../lnav.cfg --replace $(SOURCES) \
 		$(HEADERS))
 
+if !DISABLE_DOCUMENTATION
 all-local: lnav
 	env DUMP_INTERNALS_DIR=$(srcdir)/internals ./lnav Makefile
+endif
 
 install-exec-hook:
 	bash $(srcdir)/alpha-release.sh