Update environment.yml to use vtr-optimized (vtr compiled with PGO)

Signed-off-by: Dusty DeWeese <dustin.deweese@gmail.com>
Co-authored-by: Alessandro Comodi <44773360+acomodi@users.noreply.github.com>

environment.yml

@@ -2,6 +2,7 @@ name: symbiflow_arch_def_base
 channels:
   - defaults
   - litex-hub
+  - conda-forge
 dependencies:
   - litex-hub::capnproto-java=0.1.5_0012_g44a8c1e=20201104_165332
   - litex-hub::gcc-riscv64-elf-newlib=9.2.0=20201119_154229
@@ -11,7 +12,7 @@ dependencies:
   - litex-hub::symbiflow-yosys-plugins=1.0.0_7_g59ff1e6_23_g3a95697_17_g00b887b_0194_g40efa51=20201120_145821
   - litex-hub::prjxray-tools=0.1_2697_g0f939808=20201120_145821
   - litex-hub::prjxray-db=0.0_0239_gd87c844=20201120_145821
-  - litex-hub::vtr=v8.0.0_3015_gd912bdb88=20201210_100534
+  - litex-hub::vtr-optimized=v8.0.0_3049_g64d15e2dd=20201216_065815
   - litex-hub::yosys=0.9_5007_g2116c585=20201202_112618
   - litex-hub::zachjs-sv2v=0.0.5_0025_ge9f9696=20201120_205532
   - cmake