Add support for FSDB (#1072)

vcs.mk

@@ -1,4 +1,14 @@
+HELP_COMPILATION_VARIABLES += \
+"   USE_FSDB               = set to '1' to build VCS simulator to emit FSDB instead of VPD."
+
+HELP_SIMULATION_VARIABLES += \
+"   USE_FSDB               = set to '1' to run VCS simulator emitting FSDB instead of VPD."
+
+ifdef USE_FSDB
+WAVEFORM_FLAG=+fsdbfile=$(sim_out_name).fsdb
+else
 WAVEFORM_FLAG=+vcdplusfile=$(sim_out_name).vpd
+endif
 
 # If ntb_random_seed unspecified, vcs uses 1 as constant seed.
 # Set ntb_random_seed_automatic to actually get a random seed
@@ -55,3 +65,7 @@ PREPROC_DEFINES = \
 	+define+RANDOMIZE_REG_INIT \
 	+define+RANDOMIZE_GARBAGE_ASSIGN \
 	+define+RANDOMIZE_INVALID_ASSIGN
+
+ifdef USE_FSDB
+PREPROC_DEFINES += +define+FSDB
+endif