build: officially deprecate waf

While the waf build has served us well for many years, it's time to
officially consider it deprecated. The meson build was added fully with
the intention to eventually replace waf and its current state is more
than good enough to do that. Let's start the deprecation period now to
give users a heads up to switch before we remove waf for good.

.github/ISSUE_TEMPLATE/4_bug_report_build.md

@@ -2,7 +2,7 @@
 name: 'Report a build Problem'
 about: 'Create a report for a build related Issue'
 title: ''
-labels: 'core:waf'
+labels: 'core:meson'
 assignees: ''
 
 ---
@@ -24,7 +24,7 @@ differs from your own.
 
 ### Log file
 
-Upload build/config.log or ./waf configure output to https://0x0.st/ or attach
+Upload meson-logs/meson-log.txt or meson setup build output to https://0x0.st/ or attach
 it to the github issue, and replace this text with a link to it.
 
 The issue will be closed for ignoring the issue template.

README.md

@@ -80,6 +80,9 @@ can be obtained from your distro or PyPI. Waf can be downloaded by using the
 with mpv. Some documentation about the differences between the build systems are
 located in [build-system-differences][build-system-differences].
 
+**Note**: Building with waf is considered *deprecated* and will be removed in the
+future.
+
 ### Meson
 
 After creating your build directory (e.g. `meson setup build`), you can view a list

wscript

@@ -1063,6 +1063,8 @@ def configure(ctx):
         ctx.env.LINKFLAGS += ['-rdynamic']
 
     ctx.store_dependencies_lists()
+    from waflib import Logs
+    Logs.error("WARNING: Building mpv with waf is deprecated and will be removed the future! It is recommended to switch to meson as soon as possible.")
 
 def __write_version__(ctx):
     ctx.env.VERSIONH_ST = '--versionh="%s"'