In order to set up the Apache httpd server, we need to locate both the
httpd binary and its default module path. This is done with a hardcoded
list of locations that we scan. While this works okayish with distros
that more-or-less follow the Filesystem Hierarchy Standard, it falls
apart on others like NixOS that don't.

While it is possible to specify these paths via `LIB_HTTPD_PATH` and
`LIB_HTTPD_MODULE_PATH`, it is not a nice experience for the developer
to figure out how to set those up. And in fact we can do better by
dynamically detecting both httpd and its module path at runtime:

    - The httpd binary can be located via PATH.

    - The module directory can (in many cases) be derived via the
      `HTTPD_ROOT` compile-time variable.

Amend the code to do so. The new runtime-detected paths will only be
used in case none of the hardcoded paths are usable.

Signed-off-by: Patrick Steinhardt <redacted>
---
 t/lib-httpd.sh | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/t/lib-httpd.sh b/t/lib-httpd.sh
index 5fe3c8ab69d..26c1632ea9a 100644
--- a/t/lib-httpd.sh
+++ b/t/lib-httpd.sh

@@ -55,7 +55,7 @@ fi
 
 HTTPD_PARA=""
 
-for DEFAULT_HTTPD_PATH in '/usr/sbin/httpd' '/usr/sbin/apache2'
+for DEFAULT_HTTPD_PATH in '/usr/sbin/httpd' '/usr/sbin/apache2' "$(command -v httpd)"
 do
 	if test -x "$DEFAULT_HTTPD_PATH"
 	then

@@ -63,11 +63,17 @@ do
 	fi
 done
 
+if test -x "$DEFAULT_HTTPD_PATH"
+then
+	DETECTED_HTTPD_ROOT="$("$DEFAULT_HTTPD_PATH" -V | sed -n 's/^ -D HTTPD_ROOT="\(.*\)"$/\1/p')"
+fi
+
 for DEFAULT_HTTPD_MODULE_PATH in '/usr/libexec/apache2' \
 				 '/usr/lib/apache2/modules' \
 				 '/usr/lib64/httpd/modules' \
 				 '/usr/lib/httpd/modules' \
-				 '/usr/libexec/httpd'
+				 '/usr/libexec/httpd' \
+				 "${DETECTED_HTTPD_ROOT:+${DETECTED_HTTPD_ROOT}/modules}"
 do
 	if test -d "$DEFAULT_HTTPD_MODULE_PATH"
 	then

-- 
2.42.0