Add note on how to install java on gentoo

java/install_gentoo.txt

@@ -0,0 +1,38 @@
+sudo emerge -1 dev-java/java-config
+
+# NOTE: All of these commands rely on a same-version sdk not previously being installed
+
+# TODO: Try setting JAVA_PKG_FORCE_VM=openjdk-8, and setting JAVA_HOME manually
+sudo rsync -rvP build/install-icedtea8/ /opt/icedtea8
+cat << 'EOF' | sudo tee /usr/share/java-config-2/vm/openjdk-8 > /dev/null
+JAVA_HOME=/opt/icedtea8
+PATH="${JAVA_HOME}/bin"
+LDPATH=
+PROVIDES_TYPE='JDK JRE'
+PROVIDES_VERSION=1.8
+GENERATION=2
+EOF
+sudo emerge --buildpkg=n -O1 dev-java/openjdk:8
+sudo rm -rf /opt/icedtea8
+sudo emerge dev-java/openjdk:8
+
+sudo rsync -rvP build/install-jdk11/ /opt/jdk11
+sudo JAVA_HOME="$(echo /opt/jdk11/jvm/*/)" emerge --buildpkg=n -O1 dev-java/openjdk:11
+sudo rm -rf /opt/jdk11
+sudo emerge dev-java/openjdk:11
+
+sudo rsync -rvP build/install-jdk17/ /opt/jdk17
+sudo mkdir -p /var/db/pkg/dev-java/openjdk-bin-17
+echo 17 | sudo tee /var/db/pkg/dev-java/openjdk-bin-17/SLOT > /dev/null
+sudo ln -s /opt/jdk17/jvm/*/ /opt/openjdk-bin-17
+sudo emerge --buildpkg=n -O1 dev-java/openjdk:17
+sudo rm -rf /opt/jdk17 /opt/openjdk-bin-17 /var/db/pkg/dev-java/openjdk-bin-17
+sudo emerge dev-java/openjdk:17
+
+sudo rsync -rvP build/install-jdk21/ /opt/jdk21
+sudo mkdir -p /var/db/pkg/dev-java/openjdk-bin-21
+echo 21 | sudo tee /var/db/pkg/dev-java/openjdk-bin-21/SLOT > /dev/null
+sudo ln -s /opt/jdk21/jvm/*/ /opt/openjdk-bin-21
+sudo emerge --buildpkg=n -O1 dev-java/openjdk:21
+sudo rm -rf /opt/jdk21 /opt/openjdk-bin-21 /var/db/pkg/dev-java/openjdk-bin-21
+sudo emerge dev-java/openjdk:21