pnetlib doesn't compile

Chris,

DotGNU.XmlRpc seems to have broken building pnetlib.  When doing a build
on a clean machine I get:

Building project `pnetlib DotGNU.XmlRpc'
Building target `all' for project `pnetlib DotGNU.XmlRpc'
/usr/bin/cscc -fplugin-cs-path=/usr/lib/cscc/plugins/cscc-cs -o
./DotGNU.XmlRpc.dll -g -funsafe -nostdlib -O2 -DINSTALL_AS_DEFAULT
-DNON_ECMA -DCONFIG_FRAMEWORK_1_2 -DCONFIG_REFLECTION
-DCONFIG_RUNTIME_INFRA -DCONFIG_EXTENDED_NUMERICS -DCONFIG_DEBUG_LINES
-DCONFIG_REMOTING -DCONFIG_SERIALIZATION -DCONFIG_REFLECTION_EMIT
-DCONFIG_COM_INTEROP -DCONFIG_CODEDOM -DCONFIG_CRYPTO
-DCONFIG_X509_CERTIFICATES -DCONFIG_PERMISSIONS -DCONFIG_POLICY_OBJECTS
-DCONFIG_EXTENDED_DIAGNOSTICS -DCONFIG_WIN32_SPECIFICS
-DCONFIG_ISOLATED_STORAGE -DCONFIG_COMPONENT_MODEL
-DCONFIG_COMPONENT_MODEL_DESIGN -DCONFIG_EXTENDED_CONSOLE -DCONFIG_SSL
-DCONFIG_SERIAL_PORTS -DDEBUG -DTRACE -fassembly-version=1.2.3400.0
-Wno-empty-input -fminimize-parameters -flatin1-charset ./XmlRpcArray.cs
./XmlRpcClientProtocol.cs ./XmlRpcException.cs ./XmlRpcMethod.cs
./XmlRpcObject.cs ./XmlRpcRequest.cs ./XmlRpcResponse.cs
./XmlRpcStruct.cs ./XmlRpcWriter.cs ./Serialization/IXmlRpcMessage.cs
./Serialization/MethodCallFormatter.cs
./Serialization/MethodResponseFormatter.cs -L./../System -lSystem
could not locate the assembly mscorlib/1.2.3400.0
./../System/System.dll: unresolved external references
*** Target `all' for project `pnetlib DotGNU.XmlRpc' failed ***
*** Project `pnetlib DotGNU.XmlRpc' build failed ***
make[1]: *** [DotGNU.XmlRpc.dll] Error 1
make[1]: Leaving directory
`/usr/src/redhat/BUILD/pnetlib-0.6.5a/DotGNU.XmlRpc'
make: *** [all-recursive] Error 1
error: Bad exit status from /var/tmp/rpm-tmp.46038 (%build)