[lmi] Experimental 'shellcheck' patch for cygwin

[Greg Chicares]

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diff --git a/check_script.sh b/check_script.sh
index ebfddb8c..1bfe7fe3 100755
--- a/check_script.sh
+++ b/check_script.sh
@@ -21,9 +21,16 @@
 # email: <address@hidden>
 # snail: Chicares, 186 Belle Woods Drive, Glastonbury CT 06033, USA
 
+# Do nothing for cygwin, which has no 'shellcheck' package.
+
+lmi_build_type=$(/usr/share/libtool/build-aux/config.guess)
+case "$lmi_build_type" in
+  (*-*-cygwin*) exit 0 ;;
+esac
+
 # Skip:
 #  - empty argument: no script to check
-#  - git's default hooks: the maintainers don't use shellcheck
+#  - git's default hooks: the maintainers don't use 'shellcheck'
 #  - tabs/ scripts: they're extraordinary
 
 case "$1" in
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