No-Inherit is a little windows utility I whipped up for use with Cygwin to fix a few issues while executing windows-based programs to run a child program natively, without inheriting the parent process' environment. Use it how you want!

no-inherit.cpp

/*
 * Windows utility that creates a child process without inheriting any
 * sort of environment. Used in the setup scripts to fake a vanilla
 * windows environment for CMake.
 *
 * Developed by Qix
 */

#pragma comment(lib, "Userenv.lib")
#pragma comment(lib, "Advapi32.lib")

#include <Windows.h>
#include <cstdio>
#include <userenv.h>
#include <sstream>

#define PRINTMSG(fmt, ...) {printf("! - <%d> " fmt "\n", GetLastError(), __VA_ARGS__);\
	LPSTR buf = 0;\
	FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM|FORMAT_MESSAGE_ALLOCATE_BUFFER, NULL, GetLastError(), 0, (LPSTR)&buf, 0, 0);\
	printf("\t%s\n", buf);\
	LocalFree(buf);}

#define PRINTMSGR(fmt, ...) {PRINTMSG(fmt, __VA_ARGS__); return 1;}

int GetExitCodeProcessSmart(HANDLE, DWORD*);

int main(int argc, char** argv)
{
	// Create a security token
	HANDLE secToken;
	if(!OpenProcessToken(	GetCurrentProcess(),
							TOKEN_QUERY | TOKEN_IMPERSONATE,
							&secToken))
		PRINTMSGR("Could not lease process token!");

	// Create environment block
	void* envBlock = 0;
	if(!CreateEnvironmentBlock(&envBlock, secToken, FALSE))
		PRINTMSGR("Could not create non-inherited environment block!");

	// Close security token
	if(!CloseHandle(secToken))
		PRINTMSG("WARNING: Could not close security handle!");

	// Do we have args?
	std::stringstream ss;
	if(argc > 1)
	{
		// Collapse
		for(int i = 1; i < argc; i++)
			ss << (i == 1 ? "" : " ") << argv[i];
	} else {
		printf("! - No command specified!\n");
		return 2;
	}

	// Get startup info
	STARTUPINFOA info;
	ZeroMemory(&info, sizeof(info));
	info.cb = sizeof(info);

	// Create process
	PROCESS_INFORMATION proc;
	if(!CreateProcessA(	NULL,
						(LPSTR)ss.str().c_str(),
						NULL,
						NULL,
						FALSE,
						CREATE_DEFAULT_ERROR_MODE |
						CREATE_NEW_PROCESS_GROUP |
						CREATE_UNICODE_ENVIRONMENT,
						envBlock,
						NULL,
						&info,
						&proc))
		PRINTMSGR("Could not create non-inherited child process!!");

	// Wait for return
	int finalResult = -1;
	DWORD returnCode = 0;
	while((finalResult = GetExitCodeProcessSmart(proc.hProcess, &returnCode)) == 0)
		Sleep(50);

	// Was was the final result?
	if(finalResult == -1)
		PRINTMSGR("Failed when waiting for process to exit");

	// Return
	return returnCode;
}

// Below function credits to bionicbeagle over at MSDN
int GetExitCodeProcessSmart(HANDLE hProcess, DWORD* pdwOutExitCode)
{
    //Get exit code for the process
    //'hProcess' = process handle
    //'pdwOutExitCode' = if not NULL, receives the exit code (valid only if returned 1)
    //RETURN:
    //= 1 if success, exit code is returned in 'pdwOutExitCode'
    //= 0 if process has not exited yet
    //= -1 if error, check GetLastError() for more info
    int nRes = -1;

    DWORD dwExitCode = 0;
    if(::GetExitCodeProcess(hProcess, &dwExitCode))
    {
        if(dwExitCode != STILL_ACTIVE)
        {
            nRes = 1;
        }
        else
        {
            //Check if process is still alive
            DWORD dwR = ::WaitForSingleObject(hProcess, 0);
            if(dwR == WAIT_OBJECT_0)
            {
                nRes = 1;
            }
            else if(dwR == WAIT_TIMEOUT)
            {
                nRes = 0;
            }
            else
            {
                //Error
                nRes = -1;
            }
        }
    }

    if(pdwOutExitCode)
        *pdwOutExitCode = dwExitCode;

    return nRes;
}