Fix weak attribute position

Author: gchatelet

ortools/linear_solver/linear_solver.cc

@@ -412,8 +412,8 @@ MPSolver::MPSolver(const std::string& name,
 
 MPSolver::~MPSolver() { Clear(); }
 
-bool GurobiIsCorrectlyInstalled() __attribute__((weak)) { return false; }
-bool XpressIsCorrectlyInstalled() __attribute__((weak)) { return false; }
+bool __attribute__((weak)) GurobiIsCorrectlyInstalled() { return false; }
+bool __attribute__((weak)) XpressIsCorrectlyInstalled() { return false; }
 
 // static
 bool MPSolver::SupportsProblemType(OptimizationProblemType problem_type) {