all common_pdn.tcl configs are now configurable

sky130/openlane/common_pdn.tcl

diff --git a/sky130/openlane/common_pdn.tcl b/sky130/openlane/common_pdn.tcl
index 4f52289..d0bc6b4 100644
--- a/sky130/openlane/common_pdn.tcl
+++ b/sky130/openlane/common_pdn.tcl
@@ -7,11 +7,11 @@
 pdngen::specify_grid stdcell {
     name grid
     rails {
-	    met1 {width $::env(PDN_RAIL_WIDTH) pitch $::env(PLACE_SITE_HEIGHT) offset 0}
+	    met1 {width $::env(PDN_RAIL_WIDTH) pitch $::env(PLACE_SITE_HEIGHT) offset $::env(PDN_RAIL_OFFSET)}
     }
     straps {
-	    met4 {width 1.6 pitch $::env(FP_PDN_VPITCH) offset $::env(FP_PDN_VOFFSET)}
-	    met5 {width 1.6 pitch $::env(FP_PDN_HPITCH) offset $::env(FP_PDN_HOFFSET)}
+	    met4 {width $::env(PDN_STRAP_VWIDTH) pitch $::env(FP_PDN_VPITCH) offset $::env(FP_PDN_VOFFSET)}
+	    met5 {width $::env(PDN_STRAP_HWIDTH) pitch $::env(FP_PDN_HPITCH) offset $::env(FP_PDN_HOFFSET)}
     }
     connect {{met1 met4} {met4 met5}}
 }

sky130/openlane/config.tcl

diff --git a/sky130/openlane/config.tcl b/sky130/openlane/config.tcl
index 60b1c08..01ce891 100755
--- a/sky130/openlane/config.tcl
+++ b/sky130/openlane/config.tcl
@@ -41,3 +41,8 @@
 set ::env(TRACKS_INFO_FILE) "$::env(PDK_ROOT)/$::env(PDK)/libs.tech/openlane/$::env(STD_CELL_LIBRARY)/tracks.info"
 
 set ::env(GLB_RT_L1_ADJUSTMENT) 0.99
+
+# Extra PDN configs
+set ::env(PDN_RAIL_OFFSET) 0
+set ::env(PDN_STRAP_VWIDTH) 1.6
+set ::env(PDN_STRAP_HWIDTH) 1.6