Clean build directories before CMake

Jenkinsfile

@@ -5,8 +5,9 @@ pipeline {
         stage('Build Linux') {
             agent { label 'linux' }
             steps {
+                cleanWs()
+
                 sh '''
-                    rm -rf build/linux
                     cmake -S . -B build/linux -G Ninja -DCMAKE_BUILD_TYPE=Release
                     cmake --build build/linux
                 '''
@@ -16,6 +17,8 @@ pipeline {
         stage('Check Windows Agent') {
             agent { label 'windows' }
             steps {
+                cleanWs()
+
                 bat '''
                     echo Windows agent works
                     hostname