back-dating the build to 20.04 for ubuntu compatibility

Author: hephaestus

.github/workflows/release.yml

@@ -7,7 +7,7 @@ on:
 
 jobs:
   linux:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
     - name: Checkout
       uses: actions/checkout@v1

build-linux.sh

@@ -45,7 +45,8 @@ echo "JavaCPP configs:"
 java -jar $SCRIPT_DIR/javacpp-platform-$JAVACPP_VER-bin/javacpp.jar -Dcompiler.includepath=$BUILDDIR/include/ -print properties.includepath
 
 java -jar $SCRIPT_DIR/javacpp-platform-$JAVACPP_VER-bin/javacpp.jar  org/mujoco/MuJoCoConfig.java
-java -jar $SCRIPT_DIR/javacpp-platform-$JAVACPP_VER-bin/javacpp.jar -copylibs -copyresources -Xcompiler "-I$JAVADIR" -Xcompiler "-L$JAVADIR" org/mujoco/MuJoCoLib.java
+echo "Start compile \n\n"
+java -jar $SCRIPT_DIR/javacpp-platform-$JAVACPP_VER-bin/javacpp.jar  -copylibs -copyresources -Xcompiler "-no-pie"  -Xcompiler "-I$JAVADIR" -Xcompiler "-L$JAVADIR" org/mujoco/MuJoCoLib.java
 LIBPATH=$PWD/../resources/$TYPE/
 mkdir -p $SCRIPT_DIR/src/main/resources/