Add builds.sr.ht configurations

Build and test (using both clang and gcc) on Debian stable x86_64,
FreeBSD and Debian unstable arm64.

.builds/debian-arm64.yml

@@ -0,0 +1,20 @@
+image: debian/unstable
+arch: arm64
+packages:
+    - clang
+    - make
+    - gcc
+tasks:
+    - clang-build: |
+        cd kakoune
+        CXX=clang++ make -j$(nproc)
+    - clang-test: |
+        cd kakoune
+        LC_ALL=C.utf8 make test
+    - gcc-build: |
+        cd kakoune
+        make clean
+        CXX=g++ make -j$(nproc)
+    - gcc-test: |
+        cd kakoune
+        LC_ALL=C.utf8 make test

.builds/debian.yml

@@ -0,0 +1,19 @@
+image: debian/stable
+packages:
+    - clang
+    - gcc
+    - make
+tasks:
+    - clang-build: |
+        cd kakoune
+        CXX=clang++ make -j$(nproc)
+    - clang-test: |
+        cd kakoune
+        LC_ALL=C.utf8 make test
+    - gcc-build: |
+        cd kakoune
+        make clean
+        CXX=g++ make -j$(nproc)
+    - gcc-test: |
+        cd kakoune
+        LC_ALL=C.utf8 make test

.builds/freebsd.yml

@@ -0,0 +1,18 @@
+image: freebsd/13.x
+packages:
+    - gmake
+    - gcc
+tasks:
+    - build-clang: |
+        cd kakoune
+        CXX=clang++ gmake -j$(sysctl -n hw.ncpu)
+    - test-clang: |
+        cd kakoune
+        LC_ALL=en_US.UTF-8 gmake test
+    - build-gcc: |
+        cd kakoune
+        gmake clean
+        CXX=g++ gmake -j$(sysctl -n hw.ncpu)
+    - test-gcc: |
+        cd kakoune
+        LC_ALL=en_US.UTF-8 gmake test

README.asciidoc

@@ -1,9 +1,11 @@
-= image:{logo}[K,30,30,link="{website}",title="Kakoune logo by p0nce"] Kakoune image:{cirrus-img}[link="{cirrus-url}"] image:{irc-img}[link="{irc-url}"]
+= image:{logo}[K,30,30,link="{website}",title="Kakoune logo by p0nce"] Kakoune image:{cirrus-img}[link="{cirrus-url}"] {srht-img}[link="{srht-url}"] image:{irc-img}[link="{irc-url}"]
 ifdef::env-github,env-browser[:outfilesuffix: .asciidoc]
 :logo: https://rawgit.com/mawww/kakoune/master/doc/kakoune_logo.svg
 :website: https://kakoune.org
 :cirrus-img: https://api.cirrus-ci.com/github/mawww/kakoune.svg
 :cirrus-url: https://cirrus-ci.com/github/mawww/kakoune
+:srht-img: https://builds.sr.ht/~mawww/kakoune.svg
+:srht-url: https://builds.sr.ht/~mawww/kakoune?
 :irc-img: https://img.shields.io/badge/IRC-%23kakoune-blue.svg
 :irc-url: https://web.libera.chat/?channels=kakoune
 :icons: font