doc: Building on Alpine Linux

Describe the required packages for building U-Boot on Alpine Linux

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>

Author: xypron

doc/build/gcc.rst

@@ -51,6 +51,16 @@ Depending on the build targets further packages maybe needed.
     zypper install bc bison flex gcc libopenssl-devel libSDL2-devel make \
       ncurses-devel python3-devel python3-pytest swig
 
+Alpine Linux
+~~~~~~~~~~~~
+
+For building U-Boot on Alpine Linux at least the following packages are needed:
+
+.. code-block:: bash
+
+    apk add alpine-sdk bc bison dtc flex linux-headers ncurses-dev \
+      openssl-dev python3 py3-setuptools python3-dev sdl2
+
 Prerequisites
 -------------