Add lock around compiling (#871)

The compiler tries to compile the same source multiple times and more
importantly write out to the same filename. Adding a lock to prevent
simultaneous compilation solves this issue. This is particularly
noticeable in integer_ops testing when using offline compilation,
but just in case, hold the lock for the entire program creation.

Signed-off-by: Mats Petersson <mats.petersson@arm.com>
Signed-off-by: Stuart Brady <stuart.brady@arm.com>

test_common/harness/kernelHelpers.cpp

@@ -28,6 +28,7 @@
 #include <fstream>
 #include <sstream>
 #include <iomanip>
+#include <mutex>
 
 #if defined(_WIN32)
 std::string slash = "\\";
@@ -35,6 +36,8 @@ std::string slash = "\\";
 std::string slash = "/";
 #endif
 
+static std::mutex gCompilerMutex;
+
 static cl_int get_first_device_id(const cl_context context, cl_device_id &device);
 
 long get_file_size(const std::string &fileName)
@@ -717,6 +720,8 @@ static int create_single_kernel_helper_create_program(cl_context context,
                                                       const bool openclCXX,
                                                       CompilationMode compilationMode)
 {
+    std::lock_guard<std::mutex> compiler_lock(gCompilerMutex);
+
     std::string filePrefix = get_unique_filename_prefix(numKernelLines,
                                                         kernelProgram,
                                                         buildOptions);