doc: add libelf-dev dependency to GSG
The new acrn-kernel for v3.1 expects gelf.h that's installed with the libelf-dev
package that's not listed as a dependency in the GSG.  Without this
package, building acrn-kernel fails.
@@ -130,7 +130,7 @@ To set up the ACRN build environment on the development computer:
python3 python3-pip python3.8-venv libblkid-dev e2fslibs-dev \
pkg-config libnuma-dev libcjson-dev liblz4-tool flex bison \
xsltproc clang-format bc libpixman-1-dev libsdl2-dev libegl-dev \
- libgles-dev libdrm-dev gnu-efi
+ libgles-dev libdrm-dev gnu-efi libelf-dev
#. Install Python package dependencies:
