Build GTK3 support for linux x86-64 to maximize compatibility

Recently all SWT builds for Linux x86-64 have been done on a new
Debian image. This leads to requiring such a new distro to be
able to run SWT successfully.

This change builds GTK3 and common code on an older debian container
to increase the range of versions we support. Only GTK4's key library,
libswt-pi4-gtk*.so is shipped from a build on the new debaian container.

We continue to build all of the natives on latest debian so we benefit
from compiler warnings/errors and other such tooling.

Prerequisite eclipse-platform/eclipse.platform.releng.aggregator#2802

Fixes eclipse-platform#1791

Jenkinsfile

@@ -17,7 +17,7 @@
 
 def runOnNativeBuildAgent(String platform, Closure body) {
 	def final nativeBuildStageName = 'Build SWT-native binaries'
-	if (platform == 'gtk.linux.x86_64') {
+	if (platform == 'gtk4.linux.x86_64') {
 		podTemplate(inheritFrom: 'basic' /* inherit general configuration */, containers: [
 			containerTemplate(name: 'swtbuild', image: 'eclipse/platformreleng-debian-swtnativebuild:12',
 				resourceRequestCpu:'1000m', resourceRequestMemory:'512Mi',
@@ -26,6 +26,15 @@ def runOnNativeBuildAgent(String platform, Closure body) {
 		]) {
 			node(POD_LABEL) { stage(nativeBuildStageName) { container('swtbuild') { body() } } }
 		}
+	} else if (platform == 'gtk.linux.x86_64') {
+		podTemplate(inheritFrom: 'basic' /* inherit general configuration */, containers: [
+			containerTemplate(name: 'swtbuild', image: 'eclipse/platformreleng-debian-swtgtk3nativebuild:10',
+				resourceRequestCpu:'1000m', resourceRequestMemory:'512Mi',
+				resourceLimitCpu:'2000m', resourceLimitMemory:'4096Mi',
+				alwaysPullImage: true, command: 'cat', ttyEnabled: true)
+		]) {
+			node(POD_LABEL) { stage(nativeBuildStageName) { container('swtbuild') { body() } } }
+		}
 	} else {
 		// See the Definition of the RelEng Jenkins instance in
 		// https://github.com/eclipse-cbi/jiro/tree/master/instances/eclipse.platform.releng
@@ -199,6 +208,7 @@ pipeline {
 						'gtk.linux.ppc64le',\
 						'gtk.linux.riscv64',\
 						'gtk.linux.x86_64',\
+						'gtk4.linux.x86_64',\
 						'win32.win32.aarch64',\
 						'win32.win32.x86_64'
 					}
@@ -220,22 +230,29 @@ pipeline {
 								runOnNativeBuildAgent("${PLATFORM}") {
 									cleanWs() // Workspace is not cleaned up by default, so we do it explicitly
 									echo "OS: ${os}, ARCH: ${arch}"
-									unstash "swt.binaries.sources.${ws}"
+									unstash "swt.binaries.sources.${ws == 'gtk4' ? 'gtk' : ws }"
 									dir('jdk.resources') {
 										unstash "jdk.resources.${os}.${arch}"
 									}
 									withEnv(['MODEL=' + arch, "OUTPUT_DIR=${WORKSPACE}/libs", "SWT_JAVA_HOME=${WORKSPACE}/jdk.resources"]) {
 										if (isUnix()){
 											sh '''
 												mkdir libs
-												if [ "${PLATFORM}" = "gtk.linux.aarch64" ]; then
+												if [[ ${PLATFORM} == gtk.linux.* ]]; then
 													sh build.sh -gtk3 install
-												elif [ "${PLATFORM}" = "gtk.linux.ppc64le" ]; then
-													sh build.sh -gtk3 install
-												elif [ "${PLATFORM}" = "gtk.linux.riscv64" ]; then
-													sh build.sh -gtk3 install
-												else
+												elif [[ ${PLATFORM} == gtk4.linux.* ]]; then
+													# We build both 3 + 4, but we only keep libswt-pi4-gtk
+													# (see 'Collect and sign binaries' stage)
+													#
+													# We build both to help catch build errors as this
+													# build runs against more modern gcc/libs and helps
+													# with verification
+													sh build.sh install
+												elif [[ ${PLATFORM} == cocoa.macosx.* ]]; then
 													sh build.sh install 
+												else
+													echo "Unexpected build platform ${PLATFORM}"
+													exit 1
 												fi
 												ls -1R libs
 											'''
@@ -259,9 +276,13 @@ pipeline {
 							dir("libs/${PLATFORM}") {
 								unstash "swt.binaries.${PLATFORM}"
 								sh '''
+									DEST_PLATFORM=${PLATFORM}
 									if [[ ${PLATFORM} == cocoa.macosx.* ]]; then
 										binariesExtension='jnilib'
 										signerUrl='https://cbi.eclipse.org/macos/codesign/sign'
+									elif [[ ${PLATFORM} == gtk4.linux.x86_64 ]]; then
+										binariesExtension='so'
+										DEST_PLATFORM=gtk.linux.x86_64
 									elif [[ ${PLATFORM} == gtk.linux.* ]]; then
 										binariesExtension='so'
 									elif [[ ${PLATFORM} == win32.win32.* ]]; then
@@ -278,7 +299,11 @@ pipeline {
 											done
 										fi
 									fi
-									cp *.$binariesExtension "${WORKSPACE}/eclipse.platform.swt/binaries/org.eclipse.swt.${PLATFORM}/"
+									if [[ ${PLATFORM} == gtk4.linux.x86_64 ]]; then
+										cp libswt-pi4-gtk*.so "${WORKSPACE}/eclipse.platform.swt/binaries/org.eclipse.swt.${DEST_PLATFORM}/"
+									else
+										cp *.$binariesExtension "${WORKSPACE}/eclipse.platform.swt/binaries/org.eclipse.swt.${DEST_PLATFORM}/"
+									fi
 								'''
 							}
 						}