Makefile: build 'gitweb' in the default target

Our Makefile's default target used to build 'gitweb', though indirectly: the 'all' target depended on 'git-instaweb', which in turn depended on 'gitweb'. Then e25c7cc146 (Makefile: drop dependency between git-instaweb and gitweb, 2015-05-29) removed the latter dependency, and for good reasons (quoting its commit message): "1. git-instaweb has no build-time dependency on gitweb; it is a run-time dependency 2. gitweb is a directory that we want to recursively make in. As a result, its recipe is marked .PHONY, which causes "make" to rebuild git-instaweb every time it is run." Since then a simple 'make' doesn't build 'gitweb'. Luckily, installing 'gitweb' is not broken: although 'make install' doesn't depend on the 'gitweb' target, it has a dependency on the 'install-gitweb' target, which does generate all the necessary files for 'gitweb' and installs them. However, if someone runs 'make && sudo make install', then those files in the 'gitweb' directory will be generated and owned by root, which is not nice. List 'gitweb' as a direct dependency of the default target, so a plain 'make' will build it. Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com> Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>