mpv: fetch waf in do_fetch

The mpv git repository doesn't include a copy of waf, instead there is a
bootstrap script to fetch it.

This recipe calls the bootstrap script in a do_patch postfunc, but
downloading should be done in do_fetch. Instead of calling
./bootstrap.sh simply add waf to the SRC_URI so that Bitbake can use the
mirrors/proxies/caching/checksum functionality.

This is both better code and also works in buildtools environments
where urllib2 can't make secure connections without configuration.

[ YOCTO #14073 ]

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Khem Raj <raj.khem@gmail.com>
(cherry picked from commit 5af46f89fc)
Signed-off-by: Armin Kuster <akuster808@gmail.com>

meta-oe/recipes-multimedia/mplayer/mpv_0.32.0.bb

@@ -18,7 +18,9 @@ LICENSE_FLAGS = "commercial"
 SRCREV_mpv = "70b991749df389bcc0a4e145b5687233a03b4ed7"
 SRC_URI = " \
     git://github.com/mpv-player/mpv;name=mpv \
+    https://waf.io/waf-2.0.20;name=waf;subdir=git \
 "
+SRC_URI[waf.sha256sum] = "bf971e98edc2414968a262c6aa6b88541a26c3cd248689c89f4c57370955ee7f"
 
 S = "${WORKDIR}/git"
 
@@ -101,14 +103,10 @@ EXTRA_OECONF = " \
     ${PACKAGECONFIG_CONFARGS} \
 "
 
-do_patch[postfuncs] += "get_waf"
-
-get_waf() {
-    cd ${S}
-    ./bootstrap.py
-    sed -i -e 's|/usr/bin/env python|/usr/bin/env python3|g' ${S}/waf
-    cd -
+link_waf() {
+    ln -s waf-2.0.20 ${S}/waf
 }
+do_unpack[postfuncs] += "link_waf"
 
 FILES_${PN} += " \
     ${datadir}/icons \