Move uncritical files into etc/ (#350)

This is mainly just to reduce the amount of files in the project root.
The criteria of what gets into `etc/` are the following:

* The file should not be necessary for building nsxiv. This excludes the
  `icon/*` stuff since that's needed by `window.c`.
* The file shouldn't have any valid reason to stay in the project root.
  This excludes things like `README.md`, `.gitignore` etc.

Reviewed-on: https://codeberg.org/nsxiv/nsxiv/pulls/350
Reviewed-by: explosion-mental <explosion-mental@noreply.codeberg.org>

etc/woodpecker/build.yml

@@ -0,0 +1,28 @@
+branches: master
+
+# NOTE: "stable" tcc is too old and fails at linking. instead fetching a recent known working commit.
+pipeline:
+  build:
+    image: alpine
+    environment:
+      - TCC_SHA=027b8fb9b88fe137447fb8bb1b61079be9702472
+    commands: |
+      apk add --no-cache \
+          imlib2 imlib2-dev xorgproto \
+          libxft libxft-dev libexif libexif-dev giflib giflib-dev libwebp libwebp-dev \
+          gcc clang llvm llvm-dev build-base wget ca-certificates >/dev/null
+      wget "https://github.com/TinyCC/tinycc/archive/$TCC_SHA.tar.gz" >/dev/null
+      tar xzf "$TCC_SHA.tar.gz" >/dev/null
+      ( cd "tinycc-$TCC_SHA" && ./configure --config-musl && make -s -j"$(nproc)" && make install; ) >/dev/null
+      CFLAGS="$(sed '/^#/d' etc/woodpecker/CFLAGS | paste -d ' ' -s)"
+      build () {
+        for cc in "gcc" "clang" "tcc"; do
+          echo "### $cc - $2 build ###"
+          make clean && make -s -j"$(nproc)" CC="$cc" CFLAGS="$CFLAGS" LDFLAGS="$CFLAGS" OPT_DEP_DEFAULT="$1"
+        done
+      }
+      # full-build #
+      build "1" "full"
+      # ensure minimal-build works without opt deps installed
+      apk del libxft libxft-dev libexif libexif-dev giflib giflib-dev libwebp libwebp-dev >/dev/null
+      build "0" "minimal"