doc/build/gcc: add more required packages

The following Python packages are used by U-Boot, too:

* python3-asteval
* python3-subunit
* python3-testtools
Signed-off-by: NHeinrich Schuchardt <heinrich.schuchardt@canonical.com>

doc/build/gcc.rst

@@ -27,10 +27,10 @@ Depending on the build targets further packages maybe needed
       device-tree-compiler dfu-util efitools flex gdisk graphviz imagemagick \
       liblz4-tool libgnutls28-dev libguestfs-tools libncurses-dev \
       libpython3-dev libsdl2-dev libssl-dev lz4 lzma lzma-alone openssl \
-      pkg-config python3 python3-coverage python3-pkg-resources \
-      python3-pycryptodome python3-pyelftools python3-pytest \
-      python3-sphinxcontrib.apidoc python3-sphinx-rtd-theme python3-virtualenv \
-      swig
+      pkg-config python3 python3-asteval python3-coverage \
+      python3-pkg-resources python3-pycryptodome python3-pyelftools \
+      python3-pytest python3-sphinxcontrib.apidoc python3-sphinx-rtd-theme \
+      python3-subunit python3-testtools python3-virtualenv swig
 
 SUSE based
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