Add Amazon Linux 2 support, prepare for PG18

* Add Amazon Linux 2 as a supported OS.

* Dynamically select the package manager for Amazon and Oracle Linux.

* Prepare for supporting PostgreSQL 18.  Specifically, the Docker image
  seems to have moved the data directory, so get that dynamically.

Makefile

@@ -42,6 +42,7 @@ SUPPORTED := ubuntu-20.04 \
 	     rockylinux-9 \
 	     rockylinux-10 \
 	     oraclelinux-7 \
+	     amazonlinux-2 \
 	     amazonlinux-2023 \
 	     gentoo
 
@@ -219,18 +220,21 @@ ubuntu-%-install-test:
 	     bash -c 'apt-get update && apt-get install -y /output/$(PACKAGE_NAME)-$(DEB_VERSION)-ubuntu-$*.deb'
 
 # Run an OracleLinux install test (this is for EL7 since CentOS7 images no longer exist)
+oraclelinux-%-install-test: MGR=$(intcmp $*, 7, yum, yum, dnf)
 oraclelinux-%-install-test:
 	docker run --rm \
 	     -v ./$(BUILD_DIR):/output \
-	     oraclelinux:7 \
-	     bash -c 'yum makecache && yum install -y /output/$(PACKAGE_NAME)-$(RPM_VERSION).el7.noarch.rpm'
+	     oraclelinux:$* \
+	     bash -c '$(MGR) makecache && $(MGR) install -y /output/$(PACKAGE_NAME)-$(RPM_VERSION).el7.noarch.rpm'
 
 # Run a Amazon Linux install test
+# Note: AL2 is too old for dnf
+amazonlinux-%-install-test: MGR=$(intcmp $*, 2, yum, yum, dnf)
 amazonlinux-%-install-test:
 	docker run --rm \
 	     -v ./$(BUILD_DIR):/output \
 	     amazonlinux:$* \
-	     bash -c 'dnf makecache && dnf install -y /output/$(PACKAGE_NAME)-$(RPM_VERSION).amzn$*.noarch.rpm'
+	     bash -c '$(MGR) makecache && $(MGR) install -y /output/$(PACKAGE_NAME)-$(RPM_VERSION).amzn$*.noarch.rpm'
 
 # Run a Gentoo install test
 gentoo-install-test: