updating readme, setting up rpath for qcor compiler wrapper

Signed-off-by: Alex McCaskey <mccaskeyaj@ornl.gov>

README.md

@@ -34,6 +34,60 @@ $ mkdir build && cd build
 $ cmake .. -DXACC_DIR=~/.xacc (or wherever you installed XACC)
 $ make install
 ```
+Update your PATH to ensure that the ```qcor``` compiler is available.
+```bash
+$ export PATH=$PATH:$HOME/.xacc/bin
+```
 
 To target IBM, Rigetti, or TNQVM, please also build the
-corresponding XACC plugins. See https://xacc.readthedocs.io/en/latest/plugins.html.
\ No newline at end of file
+corresponding XACC plugins. See https://xacc.readthedocs.io/en/latest/plugins.html.
+
+## Example Usage
+
+Here we demonstrate how to program, compile, and run the Deuteron H2 VQE problem. Create
+the following file
+
+```cpp
+#include "qcor.hpp"
+
+int main() {
+
+  // Initialize the QCOR Runtime
+  qcor::Initialize({"--accelerator", "tnqvm"});
+
+  // Create an Optimizer, default is NLOpt COBYLA
+  auto optimizer = qcor::getOptimizer("nlopt");
+
+  // Create the Deuteron Observable
+  const std::string deuteronH2 =
+      R"deuteronH2((5.907,0) + (-2.1433,0) X0 X1 + (-2.1433,0) Y0 Y1 + (.21829,0) Z0 + (-6.125,0) Z1)deuteronH2";
+  PauliOperator op;
+  op.fromString(deuteronH2);
+
+  // Schedule an asynchronous VQE execution
+  // with the given quantum kernel ansatz
+  auto future = qcor::submit([&](qcor::qpu_handler &qh) {
+    qh.vqe(
+        [&](double t0) {
+          X(0);
+          Ry(t0, 1);
+          CX(1, 0);
+        },
+        op, optimizer);
+  });
+
+  // Get and print the results
+  auto results = future.get();
+  results->print();
+}
+```
+To compile this with QCOR, run the following
+
+```bash
+$ qcor deuteron.cpp -o deuteron
+```
+This will create the ```deuteron``` quantum-classical binary executable.
+Now just run
+```bash
+$ ./deuteron
+```
\ No newline at end of file

compiler/clang/CMakeLists.txt

@@ -15,5 +15,11 @@ target_include_directories(${LIBRARY_NAME}
                                   ${XACC_INCLUDE_ROOT}/cppmicroservices4)
 target_link_libraries(${LIBRARY_NAME}
                       PUBLIC ${CLANG_LIBS} ${XACC_LIBRARIES} qcor)
-
+if(APPLE)
+   set_target_properties(${LIBRARY_NAME} PROPERTIES INSTALL_RPATH "@loader_path")
+   set_target_properties(${LIBRARY_NAME} PROPERTIES LINK_FLAGS "-undefined dynamic_lookup")
+else()
+   set_target_properties(${LIBRARY_NAME} PROPERTIES INSTALL_RPATH "$ORIGIN")
+   set_target_properties(${LIBRARY_NAME} PROPERTIES LINK_FLAGS "-shared")
+endif()
 install(TARGETS ${LIBRARY_NAME} DESTINATION lib)

runtime/nlopt-optimizers/CMakeLists.txt

@@ -19,7 +19,7 @@ target_include_directories(
   ${LIBRARY_NAME}
   PUBLIC . .. ${CMAKE_BUILD_DIR}/runtime/nlopt-optimizers/nlopt/src/api)
 
-target_link_libraries(${LIBRARY_NAME} PUBLIC nlopt)
+target_link_libraries(${LIBRARY_NAME} PUBLIC nlopt CppMicroServices)
 
 set(_bundle_name qcor_runtime_nlopt)
 set_target_properties(${LIBRARY_NAME}

scripts/qcor.in

@@ -3,6 +3,7 @@ import argparse
 import sys
 import subprocess
 
+
 def parse_args(args):
     parser = argparse.ArgumentParser(description="QCOR Quantum-Classical C++ Compiler.",
                                      formatter_class=argparse.ArgumentDefaultsHelpFormatter,
@@ -26,7 +27,7 @@ def parse_args(args):
 def main(argv=None):
     opts = parse_args(sys.argv[1:])
 
-    command = ["@CLANG_COMPILER@", '-std=c++11', '-Xclang', '-load', '-Xclang', '@CMAKE_INSTALL_PREFIX@/lib/libqcor-ast-plugin.so',
+    command = ["@CLANG_COMPILER@", '-std=c++11', '-Wl,-rpath,@CMAKE_INSTALL_PREFIX@/lib', '-Xclang', '-load', '-Xclang', '@CMAKE_INSTALL_PREFIX@/lib/libqcor-ast-plugin.so',
                '-Xclang', '-add-plugin', '-Xclang', 'enable-quantum']
     if opts.accelerator:
         command += ['-plugin-arg-enable-quantum', '-Xclang', 'accelerator', '-Xclang',