add check that that extension module is compiled before running example scripts

tools/swig/run_java_example.sh

@@ -1,5 +1,11 @@
 #!/bin/sh
 
+if [ ! -f libjavalammps.so ]
+then \
+    echo "Need to compile 'libjavalammps.so' first for this script to work"
+    exit 1
+fi
+
 cat > example.java <<EOF
 public class example {
   static {

tools/swig/run_lua_example.sh

@@ -1,5 +1,11 @@
 #!/bin/sh
 
+if [ ! -f lualammps.so ]
+then \
+    echo "Need to compile 'lualammps.so' first for this script to work"
+    exit 1
+fi
+
 cat > example.lua <<EOF
 require("lualammps")
 

tools/swig/run_perl_example.sh

@@ -1,5 +1,11 @@
 #!/bin/sh
 
+if [ ! -f pllammps.so ]
+then \
+    echo "Need to compile 'pllammps.so' first for this script to work"
+    exit 1
+fi
+
 cat > example.pl <<EOF
 use pllammps;
 

tools/swig/run_python_example.sh

@@ -1,5 +1,11 @@
 #!/bin/sh
 
+if [ ! -f _pylammps.so ]
+then \
+    echo "Need to compile '_pylammps.so' first for this script to work"
+    exit 1
+fi
+
 cat > example.py <<EOF
 from pylammps import *
 

tools/swig/run_ruby_example.sh

@@ -1,5 +1,11 @@
 #!/bin/sh
 
+if [ ! -f rubylammps.so ]
+then \
+    echo "Need to compile 'rubylammps.so' first for this script to work"
+    exit 1
+fi
+
 cat > example.rb <<EOF
 require 'rubylammps'
 

tools/swig/run_tcl_example.sh

@@ -1,5 +1,11 @@
 #!/bin/sh
 
+if [ ! -f tcllammps.so ]
+then \
+    echo "Need to compile 'tcllammps.so' first for this script to work"
+    exit 1
+fi
+
 cat > example.tcl <<EOF
 load ./tcllammps.so