Fix inject problems (#820)

* CoreCLR: resolve and load nethost on demand instead of requiring it on load

* Remove nethost loading from C# side

* Added option to not chain Process.Dispose; see for last error only if result is empty

lib/CoreCLR/nethost/nethost.h

@@ -6,36 +6,6 @@
 
 #include <stddef.h>
 
-#ifdef _WIN32
-    #ifdef NETHOST_EXPORT
-        #define NETHOST_API __declspec(dllexport)
-    #else
-        // Consuming the nethost as a static library
-        // Shouldn't export attempt to dllimport.
-        #ifdef NETHOST_USE_AS_STATIC
-            #define NETHOST_API 
-        #else
-            #define NETHOST_API __declspec(dllimport)
-        #endif
-    #endif
-
-    #define NETHOST_CALLTYPE __stdcall
-    #ifdef _WCHAR_T_DEFINED
-        typedef wchar_t char_t;
-    #else
-        typedef unsigned short char_t;
-    #endif
-#else
-    #ifdef NETHOST_EXPORT
-        #define NETHOST_API __attribute__((__visibility__("default")))
-    #else
-        #define NETHOST_API
-    #endif
-
-    #define NETHOST_CALLTYPE
-    typedef char char_t;
-#endif
-
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -87,10 +57,10 @@ struct get_hostfxr_parameters {
 //   The full search for the hostfxr library is done on every call. To minimize the need
 //   to call this function multiple times, pass a large buffer (e.g. PATH_MAX).
 //
-NETHOST_API int NETHOST_CALLTYPE get_hostfxr_path(
-    char_t * buffer,
-    size_t * buffer_size,
-    const struct get_hostfxr_parameters *parameters);
+using get_hostfxr_path_type = int(__stdcall *)(
+    char_t* buffer,
+    size_t* buffer_size,
+    const struct get_hostfxr_parameters* parameters);
 
 #ifdef __cplusplus
 } // extern "C"