Fix incorrectly linted build command (#709)

Author: vloncar

hls4ml/backends/vivado/vivado_backend.py

@@ -189,13 +189,13 @@ def build(
         curr_dir = os.getcwd()
         os.chdir(model.config.get_output_dir())
         vivado_cmd = (
-            f'vivado_hls -f build_prj.tcl "reset={reset}'
-            f'csim={csim}'
-            f'synth={synth}'
-            f'cosim={cosim}'
-            f'validation={validation}'
-            f'export={export}'
-            f'vsynth={vsynth}'
+            f'vivado_hls -f build_prj.tcl "reset={reset} '
+            f'csim={csim} '
+            f'synth={synth} '
+            f'cosim={cosim} '
+            f'validation={validation} '
+            f'export={export} '
+            f'vsynth={vsynth} '
             f'fifo_opt={fifo_opt}"'
         )
         os.system(vivado_cmd)