INSTALL.md update for Cygwin OK.

.github/workflows/cygwin.yml

@@ -14,3 +14,6 @@ jobs:
     - name: Build
       shell: bash {0}
       run: make && make docs
+    - name: Check
+      shell: bash {0}
+      run: ldd proxytunnel.exe | awk '{print $3}' | grep -v WINDOWS | sort | uniq

INSTALL.md

@@ -94,11 +94,11 @@ me@mymachine MSYS ~ cp  /usr/bin/msys-2.0.dll /usr/bin/msys-crypto-1.1.dll /usr/
 
 # Cygwin :
 
-Install from [cygwin web site](https://cygwin.com).
+Install Cygwin from [cygwin web site](https://cygwin.com).
 
 Following packages are required :
 ```
-$ setup-x86_64.exe -n -q -P gcc-core,make,libssl-devel,zip,xmlto,asciidoc
+$ setup-x86_64.exe -n -q -P gcc-core,make,binutils,libssl-devel,xmlto,asciidoc
 ```
 
 To build :

docs/Makefile

@@ -21,7 +21,7 @@ clean:
 	asciidoc -d manpage -arevnumber=$(version) -arevdate=$(version_date) $<
 
 %.1: %.1.xml
-	xmlto man $<
+	xmlto --skip-validation man $<
 
 %.html: %.adoc
 	asciidoc $<