Process: Use more rawStd{Out,Err} const methods instead of mutable ones

Avoid using readAllStandard{Output,Error} mutable methods if possible.
Use non-mutable methods when we are not connected to
readyReadStandard{Output,Error} signals.

Change-Id: I2e830e571b9eab2177fd856bbe06dfc5137d9c01
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/mesonprojectmanager/mesonwrapper.h

@@ -42,7 +42,7 @@ inline bool run_meson(const Command &command, QIODevice *output = nullptr)
     if (!process.waitForFinished())
         return false;
     if (output) {
-        output->write(process.readAllRawStandardOutput());
+        output->write(process.rawStdOut());
     }
     return process.exitCode() == 0;
 }