Apply patch to allow users to change path of lock file (#4649)

See - https://github.com/Microsoft/CNTK/issues/62

var/spack/repos/builtin/packages/cntk/lock-file.patch

@@ -0,0 +1,20 @@
+diff --git a/Source/Common/CrossProcessMutex.h b/Source/Common/CrossProcessMutex.h
+index 2f3ce70..f0fcd42 100644
+--- a/Source/Common/CrossProcessMutex.h
++++ b/Source/Common/CrossProcessMutex.h
+@@ -127,9 +127,13 @@ class CrossProcessMutex
+
+ public:
+     CrossProcessMutex(const std::string& name)
+-        : m_fd(-1),
+-          m_fileName("/var/lock/" + name)
++        : m_fd(-1)
+     {
++        const char * const envLockDir = getenv("CNTK_LOCK_DIR");
++        if (envLockDir != NULL)
++            m_fileName = envLockDir + ('/' + name);
++        else
++            m_fileName = "/var/lock/" + name;
+     }
+
+     // Acquires the mutex. If 'wait' is true and mutex is acquired by someone else then

var/spack/repos/builtin/packages/cntk/package.py

@@ -64,6 +64,8 @@ class Cntk(Package):
     patch('build.patch')
     # Patch to fix BLAS inconsistency between CNTK and KaldiReader
     patch('kaldireader-openblas.patch')
+    # Patch to change behaviour of lock file - https://github.com/Microsoft/CNTK/issues/62
+    patch('lock-file.patch')
 
     def install(self, spec, prefix):
         args = []