fix: update Dockerfile.linuxcross to use armhf repository for toolchain

Author: robertsLando

Dockerfile.linuxcross

@@ -11,7 +11,7 @@ RUN apt-get install -y curl software-properties-common ca-certificates gnupg
 RUN curl -fsSL https://deb.nodesource.com/setup_20.x | bash - && \
     apt-get install -y nodejs
 
-RUN add-apt-repository ppa:ubuntu-toolchain-r/test -y && \
+RUN add-apt-repository ppa:ubuntu-toolchain-r/armhf -y && \
     apt-get update && \
     apt-get install -y binutils g++-10 git make patch python3 python3-distutils