build: fix tests when documentation/manual is disabled

- build: fix to exclude 'documentation' tests when building
  the documentation is explicitly disabled. Both for cmake
  and `./configure`.

  Reported-by: Daniel Engberg
  Fixes #15703

- test481, test482: fix for builds with no manual.

  Reported-by: Daniel Engberg
  Fixes #15703

- configure: fix to always detect Perl. Running tests require
  it when run. Before this patch Perl wasn't detected when
  documentation/manual/embedded-CA were all disabled,
  making tests fail to start.

- test1177: add keyword `documentation`. It depends no
  `curl_version_info.3`.

- GHA/linux: test cmake and `./configure` with docs and
  manual disabled and tests run.

Closes #15704

.github/workflows/linux.yml

@@ -119,7 +119,7 @@ jobs:
 
           - name: mbedtls-pkg
             install_packages: libnghttp2-dev libmbedtls-dev
-            generate: -DCURL_USE_MBEDTLS=ON -DENABLE_DEBUG=ON
+            generate: -DCURL_USE_MBEDTLS=ON -DENABLE_DEBUG=ON -DBUILD_LIBCURL_DOCS=OFF -DBUILD_MISC_DOCS=OFF -DENABLE_CURL_MANUAL=OFF
 
           - name: mbedtls-pkg !pc
             install_packages: libnghttp2-dev libmbedtls-dev
@@ -167,7 +167,7 @@ jobs:
 
           - name: openssl clang krb5
             install_packages: zlib1g-dev libkrb5-dev clang
-            configure: CC=clang --with-openssl --with-gssapi --enable-debug
+            configure: CC=clang --with-openssl --with-gssapi --enable-debug --disable-docs --disable-manual
 
           - name: openssl clang krb5
             install_packages: zlib1g-dev libkrb5-dev clang