I complite LibreElEC source code ,has a error

INSTALL    nss (target)
INSTALL    nss (host)      
INSTALL    nspr (target)
BUILD    expat (host)
Executing (host): cmake -GNinja -DCMAKE_EXPORT_COMPILE_COMMANDS=ON -DCMAKE_TOOLCHAIN_FILE=/home/ljb/H3/LibreELEC.tv/build.LibreELEC-Allwinner.arm-9.0-devel/toolchain/etc/cmake-x86_64-linux-gnu.conf -DCMAKE_INSTALL_PREFIX=/home/ljb/H3/LibreELEC.tv/build.LibreELEC-Allwinner.arm-9.0-devel/toolchain /home/ljb/H3/LibreELEC.tv/build.LibreELEC-Allwinner.arm-9.0-devel/expat-2.2.0
– Configuring done
– Generating done
– Build files have been written to: /home/ljb/H3/LibreELEC.tv/build.LibreELEC-Allwinner.arm-9.0-devel/expat-2.2.0/.x86_64-linux-gnu
Executing (host): ninja
ninja: error: build.ninja:155: bad $-escape (literal $ must be written as $$)

PRE_LINK = cd /home/ljb/H3/LibreELEC.tv/build.LibreELEC-Allwinner.arm-9.0-devel/expat-2.2.0/.x86_64-linux-gnu && $(MAKE) -C doc xmlwf.1 && cd /home/ljb/H3/LibreELEC.tv/build.LibreELEC-Allwinner.arm-9.0-devel/expat-2.2.0/.x86_64-linux-gnu