[rebase]: fix PATH

Author: alexcrichton

configure

@@ -1135,6 +1135,7 @@ do
             CFG_MSVC_LIB_PATH=$(cmd /c "\"$vcvarsall\" amd64 && cmd /c echo %LIB%")
             need_ok "failed to learn about MSVC's LIB"
 
+            putvar CFG_MSVC_ROOT
             putvar CFG_MSVC_CL
             putvar CFG_MSVC_LIB
             putvar CFG_MSVC_LINK

mk/cfg/x86_64-pc-windows-msvc.mk

@@ -37,7 +37,7 @@ endif
 # but it's not the one that we want. As a result we make sure that our detected
 # `link.exe` shows up in PATH first.
 ifdef CFG_MSVC_LINK
-export PATH := $(dir $(CFG_MSVC_LINK)):$(PATH)
+export PATH := $(CFG_MSVC_ROOT)/VC/bin/amd64:$(PATH)
 endif
 
 # There are more comments about this available in the target specification for