Combine OS X and Linux compiler flags.

[quantumsteve]

Description of work.

This simplifies the CMake script by setting flags for clang and gcc on OS X and Linux in a single location. I suppressed the remaining -Wcast-align warnings from Framework/ICat/src/GSoap/stdsoap2.cpp

I'm also sneaking in some fixes for -Winconsistent-missing-override warnings that are now in master.

To test:

• Check that the OS X compiler flags are still being set (I suggest using the option CMAKE_EXPORT_COMPILER_COMMANDS and viewing the json file)
• Verify that suppressing -Wcast-align warnings from Framework/ICat/src/GSoap/stdsoap2.cpp is acceptable.
• Check that Xcode still picks up the correct flags, the C++14 standard and libc++ standard library.

Fixes #11681.

Does not need to be in the release notes.

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Reviewer

Please comment on the following (full description):

Code Review

• Is the code of an acceptable quality?
• Does the code conform to the coding standards? Is it well structured with small focussed classes/methods/functions?
• Are there unit/system tests in place? Are the unit tests small and test the a class in isolation?

Functional Tests

• Do changes function as described? Add comments below that describe the tests performed?
• How do the changes handle unexpected situations, e.g. bad input?
• Has the relevant documentation been added/updated?
• Is user-facing documentation written in a user-friendly manner?
• Has developer documentation been updated if required?
• Does everything look good? Comment with the ship it emoji but don't merge. A member of @mantidproject/gatekeepers will take care of it.

[quantumsteve]

Below is another possible way to address the OS X warning. It builds and eliminates the reinterpret_cast and pointer arithmetic. I am, however, struggling to find a test to ensure it works correctly.

$ git diff
diff --git a/MantidPlot/src/MatrixModel.cpp b/MantidPlot/src/MatrixModel.cpp
index 8265d0c..65b2803 100644
--- a/MantidPlot/src/MatrixModel.cpp
+++ b/MantidPlot/src/MatrixModel.cpp
@@ -493,13 +493,13 @@ QImage MatrixModel::renderImage()
        d_matrix->range(&minValue, &maxValue);
     const QwtDoubleInterval intensityRange = QwtDoubleInterval (minValue, maxValue);
     for ( int i = 0; i < d_rows; i++ ){
-      QRgb *line = reinterpret_cast<QRgb *>(image.scanLine(i));
       for (int j = 0; j < d_cols; j++) {
-        double val = cell(i, j); // d_data[i*d_cols + j];
-        if (gsl_isnan(val))
-          *line++ = color_map.rgb(intensityRange, 0.0);
-        else if (fabs(val) < HUGE_VAL)
-          *line++ = color_map.rgb(intensityRange, val);
+        double val = cell(i, j);
+        if (gsl_isnan(val)){
+          image.setPixel(i,j,color_map.rgb(intensityRange, 0.0));
+        } else if (fabs(val) < HUGE_VAL){
+          image.setPixel(i,j,color_map.rgb(intensityRange, val));
+        }
       }
     }
     QApplication::restoreOverrideCursor();

[peterfpeterson]

The changes look reasonable.