fix premake build for linux, thanks to @consultit

See also issue #1538

examples/ThirdPartyLibs/BussIK/premake4.lua

@@ -5,6 +5,9 @@
 	includedirs {
 		"."
 	}
+    if os.is("Linux") then
+        buildoptions{"-fPIC"}
+    end
 	files {
 		"*.cpp",
 		"*.h",

examples/ThirdPartyLibs/Gwen/premake4.lua

@@ -11,6 +11,9 @@ end
 	
 	defines { "GWEN_COMPILE_STATIC"  }
 	 defines { "DONT_USE_GLUT"}	
+    if os.is("Linux") then
+        buildoptions{"-fPIC"}
+    end
 	includedirs {
 		".",".."
 	}

examples/ThirdPartyLibs/clsocket/premake4.lua

@@ -16,6 +16,9 @@
 	includedirs {
 		".","include","src"
 	}
+    if os.is("Linux") then
+        buildoptions{"-fPIC"}
+    end
 	files {
 		"src/SimpleSocket.cpp",
 		"src/ActiveSocket.cpp",

examples/ThirdPartyLibs/enet/premake4.lua

@@ -18,6 +18,9 @@
 	includedirs {
 		".","include"
 	}
+    if os.is("Linux") then
+        buildoptions{"-fPIC"}
+    end
 	files {
 		"callbacks.c",
 		"compress.c",

examples/ThirdPartyLibs/lua-5.2.3/premake4.lua

@@ -18,6 +18,9 @@
 	includedirs {
 		"src"
 	}
+    if os.is("Linux") then
+        buildoptions{"-fPIC"}
+    end
 	files {
 		"src/*.c",
 		"src/*.h"

examples/ThirdPartyLibs/serial/premake4.lua

@@ -4,6 +4,9 @@
 	
 	includedirs {"include"}
 	
+    if os.is("Linux") then
+        buildoptions{"-fPIC"}
+    end
 	if os.is("Windows") then 
 		files{
 			 "src/impl/win.cc",