RFR: JDK-8245093 WSL support broke cygwin toolchain detection

[Magnus Ihse Bursie]

Unfortunately, the fixes for WSL changed the behavior so the 
autodetection of toolchain does not work on cygwin (but providing devkit 
does work, that's why I did not discover this).

Windows and unix emulation environments are really a whack-a-mole... :(

Bug: https://bugs.openjdk.java.net/browse/JDK-8245093
Patch inline:
diff --git a/make/autoconf/basic_tools.m4 b/make/autoconf/basic_tools.m4
--- a/make/autoconf/basic_tools.m4
+++ b/make/autoconf/basic_tools.m4
@@ -97,7 +97,7 @@
    UTIL_PATH_PROGS(NICE, nice)

    UTIL_PATH_PROGS(LSB_RELEASE, lsb_release)
-  UTIL_PATH_PROGS(CMD, cmd.exe, /mnt/c/Windows/System32)
+  UTIL_PATH_PROGS(CMD, cmd.exe, $PATH /cygdrive/c/Windows/System32 
/mnt/c/Windows/System32)
  ])

  ###############################################################################

/Magnus