libvisual-plugins: Resolve troublesome "--install" from ACLOCAL_AMFLAGS

.. and remake installation of file m4/alsa.m4 for shipping.
Many thanks to Bo Anderson (@Bo98) for debugging the issue in detail.

Related:
- Homebrew/homebrew-core#217346
- https://savannah.gnu.org/bugs/?66968

This reverts commit 9b420cc.

Author: hartwork

libvisual-plugins/Makefile.am

@@ -1,6 +1,6 @@
 ## Process this file with automake to generate a Makefile.in
 
-ACLOCAL_AMFLAGS = -I m4 --install
+ACLOCAL_AMFLAGS = -I m4
 
 SUBDIRS = plugins po
 

libvisual-plugins/autogen.sh

@@ -4,9 +4,24 @@
 
 set -e -u
 
+# For alsa.m4 (with "L" in ALSA meaning "Linux") we want three things:
+# - That a build on macOS is fully okay without it.
+# - That "make dist" results from Linux contain a healthy m4/alsa.m4 file.
+# - That running ./autogen.sh (or autoreconf) on a host
+#   without ALSA development files installed still succeeds.
+alsa_m4="$(aclocal --print-ac-dir)"/alsa.m4
+if [[ -f "${alsa_m4}" ]]; then
+    mkdir -p m4/
+    cp -v "${alsa_m4}" m4/
+fi
 if [[ "$(uname -s)" == Darwin ]]; then
     # This provides a dummy substitute to alsa.m4 on macOS
+    # and that is a reason why "make dist" should be run on Linux, not macOS.
     echo 'AC_DEFUN([AM_PATH_ALSA], [HAVE_ALSA=no])' > acinclude.m4
+elif [[ ! -f m4/alsa.m4 ]]; then
+    echo "ERROR: Please install ALSA development files before running" >&2
+    echo "       '$0' on Linux." >&2
+    exit 1
 fi
 
 autoreconf --install --verbose --force || \