Cygwin curl 7.83.1 make install installs curl-config.1 twice so fails with already exists in DESTDIR

[BrianInglis]

I did this

Configure, build, and install curl in DESTDIR

I expected the following

DESTDIR populated with built files

What actually happened

make install docs/curl-config.1 installed in DESTDIR/usr/share/man/man1/ twice so install failed with message:
/usr/bin/install: cannot create regular file '.../usr/share/man/man1/curl-config.1': File exists in DESTDIR - see log for config and install details:
curl-cygport-64-all-check.log - lightly sanitized
looked in docs/Makefile but no obvious rules to use MANS twice but under install-man1 there are two loops to install pages - any ideas about possible causes or workarounds? see: build/docs/Makefile and curl-7.83.1-1-install.log - lightly sanitized

curl/libcurl version

7.83.1

operating system

Cygwin 3.3.4 under Windows 10 21H2

built with cyport 0.35.0, autoconf 2.71, automake 1.16.5

[bagder]

Is this a new bug or has this been in there for a while? I can't recall us having modified anything in this area for a long time so if something changed recently, it could be a tooling update causing it.

[BrianInglis]

7.83.0 was fine: just this update has the man install issue.
I did not find any non-trivial differences (only .0->.1) between the generated build/docs/Makefile.
When make install is run, runs Making install in ../docs:
/usr/bin/install -c -m 644 .../curl-7.83.1-1.x86_64/src/curl-7.83.1/docs/curl-config.1 .../curl-7.83.1-1.x86_64/build/docs/curl.1 '.../curl-7.83.1-1.x86_64/inst/usr/share/man/man1'
then make-recursive? runs (cd docs && make install):
/usr/bin/install -c -m 644 .../curl-7.83.1-1.x86_64/src/curl-7.83.1/docs/curl-config.1 .../curl-7.83.1-1.x86_64/build/docs/curl.1 '.../curl-7.83.1-1.x86_64/inst/usr/share/man/man1'
which appears to miss that the targets have already been installed!