Refactor dependency build scripts initialization

Rename "common" to "_init" because it not only exposes common functions
but also initializes environment variables.

Call _init in a single line in all dependency build scripts.

app/deps/_init

@@ -1,10 +1,9 @@
-#!/usr/bin/env bash
 # This file is intended to be sourced by other scripts, not executed
 
 process_args() {
     if [[ $# != 3 ]]
     then
-        # <host>: win32 or win64
+        # <host>: linux, macos, win32 or win64
         # <build_type>: native or cross
         # <link_type>: static or shared
         echo "Syntax: $0 <host> <build_type> <link_type>" >&2
@@ -12,8 +11,8 @@ process_args() {
     fi
 
     HOST="$1"
-    BUILD_TYPE="$2" # native or cross
-    LINK_TYPE="$3" # static or shared
+    BUILD_TYPE="$2"
+    LINK_TYPE="$3"
     DIRNAME="$HOST-$BUILD_TYPE-$LINK_TYPE"
 
     if [[ "$BUILD_TYPE" != native && "$BUILD_TYPE" != cross ]]

app/deps/adb_linux.sh

@@ -1,8 +1,6 @@
 #!/usr/bin/env bash
 set -ex
-DEPS_DIR=$(dirname ${BASH_SOURCE[0]})
-cd "$DEPS_DIR"
-. common
+. $(dirname ${BASH_SOURCE[0]})/_init "$@"
 
 VERSION=36.0.0
 FILENAME=platform-tools_r$VERSION-linux.zip

app/deps/adb_macos.sh

@@ -1,8 +1,6 @@
 #!/usr/bin/env bash
 set -ex
-DEPS_DIR=$(dirname ${BASH_SOURCE[0]})
-cd "$DEPS_DIR"
-. common
+. $(dirname ${BASH_SOURCE[0]})/_init "$@"
 
 VERSION=36.0.0
 FILENAME=platform-tools_r$VERSION-darwin.zip

app/deps/adb_windows.sh

@@ -1,8 +1,6 @@
 #!/usr/bin/env bash
 set -ex
-DEPS_DIR=$(dirname ${BASH_SOURCE[0]})
-cd "$DEPS_DIR"
-. common
+. $(dirname ${BASH_SOURCE[0]})/_init "$@"
 
 VERSION=36.0.0
 FILENAME=platform-tools_r$VERSION-win.zip

app/deps/dav1d.sh

@@ -1,8 +1,6 @@
 #!/usr/bin/env bash
 set -ex
-DEPS_DIR=$(dirname ${BASH_SOURCE[0]})
-cd "$DEPS_DIR"
-. common
+. $(dirname ${BASH_SOURCE[0]})/_init
 process_args "$@"
 
 VERSION=1.5.0

app/deps/ffmpeg.sh

@@ -1,8 +1,6 @@
 #!/usr/bin/env bash
 set -ex
-DEPS_DIR=$(dirname ${BASH_SOURCE[0]})
-cd "$DEPS_DIR"
-. common
+. $(dirname ${BASH_SOURCE[0]})/_init
 process_args "$@"
 
 VERSION=7.1.1

app/deps/libusb.sh

@@ -1,8 +1,6 @@
 #!/usr/bin/env bash
 set -ex
-DEPS_DIR=$(dirname ${BASH_SOURCE[0]})
-cd "$DEPS_DIR"
-. common
+. $(dirname ${BASH_SOURCE[0]})/_init
 process_args "$@"
 
 VERSION=1.0.29

app/deps/sdl.sh

@@ -1,8 +1,6 @@
 #!/usr/bin/env bash
 set -ex
-DEPS_DIR=$(dirname ${BASH_SOURCE[0]})
-cd "$DEPS_DIR"
-. common
+. $(dirname ${BASH_SOURCE[0]})/_init
 process_args "$@"
 
 VERSION=2.32.8