xbps-src: implement a 'check' stage

Add another stage 'check' between 'build' and 'install'. It is be enabled using the
variable XBPS_CHECK_PKGS=yes and disabled if unset, set to "0" or "no" in your
local etc/conf.

A new xbps-src option `-q` for `quick` will disable XBPS_CHECK_PKGS by overriding it to 0.
If enabled, `common/xbps-src/shutils/xbps-src-docheck.sh` checks for an existing
`do_check()` function in the package's template and, if it exists, calls it.

A new template variable `checkdepends` may be present and list packages required
to run the `do_check()` function. Example: `checkdepends="bc unittest-cpp"`.

common/environment/README

@@ -18,6 +18,7 @@ should be read by xbps-src:
 	* extract	(before running extract phase)
 	* configure	(before running configure phase)
 	* build		(before running build phase)
+	* check		(before running check phase)
 	* install	(before running install phase)
 	* pkg		(before running pkg phase)
 

common/environment/check/bootstrap.sh

@@ -0,0 +1 @@
+../configure/bootstrap.sh

common/environment/check/cross.sh

@@ -0,0 +1 @@
+../configure/cross.sh

common/environment/check/hardening.sh

@@ -0,0 +1 @@
+../configure/hardening.sh

common/environment/check/pkg-config.sh

@@ -0,0 +1 @@
+../configure/pkg-config.sh

common/environment/setup/sourcepkg.sh

@@ -7,7 +7,7 @@ unset -v only_for_archs distfiles checksum build_style nocross broken
 unset -v configure_script configure_args wrksrc build_wrksrc create_wrksrc
 unset -v make_cmd make_build_args make_install_args make_build_target make_install_target python_version stackage
 unset -v patch_args disable_parallel_build keep_libtool_archives
-unset -v reverts subpackages makedepends hostmakedepends depends restricted
+unset -v reverts subpackages makedepends hostmakedepends checkdepends depends restricted
 unset -v nopie build_options build_options_default bootstrap repository reverts
 unset -v CFLAGS CXXFLAGS CPPFLAGS LDFLAGS LD_LIBRARY_PATH
 unset -v CC CXX CPP GCC LD AR AS RANLIB NM OBJDUMP OBJCOPY STRIP READELF