dev-lang/gnat-gpl: rename USE=bootstrap -> USE=system-bootstrap, invert meaning

USE=bootstrap has/had a special meaning in <EAPI 5 and it also ends up
stable-masked apparently too.

It was dropped from use.desc in af748c0468
and dropped from sys-devel/gcc a while ago too (bug #440224).

To facilitate automatically using gnat-gpl in sys-devel/gcc, do two things:
* Rename USE=bootstrap -> USE=system-bootstrap
* Make USE=system-bootstrap mean "I need a working Ada compiler to build this"
  (i.e. invert its meaning) to match dev-java/openjdk and dev-lang/rust.

Bug: https://bugs.gentoo.org/137268
Bug: https://bugs.gentoo.org/440224
Bug: https://bugs.gentoo.org/547358
Bug: https://bugs.gentoo.org/919667
Signed-off-by: Sam James <sam@gentoo.org>

dev-lang/gnat-gpl/gnat-gpl-2021-r5.ebuild

@@ -24,7 +24,7 @@ GCC_TARBALL_SRC_URI="
 		-> ${MYP}.tar.gz
 	${BASE_URI}/8ace7d06e469d36d726cc8badb0ed78411e727f3?filename=${INTFDIR}.tar.gz
 		-> ${INTFDIR}.tar.gz
-	bootstrap? (
+	!system-bootstrap? (
 		amd64? (
 			${BASE_URI}/6eb6eef6bb897e4c743a519bfebe0b1d6fc409c6?filename=${BTSTRP_AMD64}.tar.gz&rand=1193
 			-> ${BTSTRP_AMD64}.tar.gz
@@ -42,7 +42,7 @@ HOMEPAGE="http://libre.adacore.com/"
 
 LICENSE+=" GPL-2 GPL-3"
 KEYWORDS="amd64 x86"
-IUSE="+ada +bootstrap"
+IUSE="+ada system-bootstrap"
 RESTRICT="test"
 
 RDEPEND="!=sys-devel/gcc-${TOOLCHAIN_GCC_PV}*"
@@ -64,7 +64,7 @@ src_prepare() {
 		BTSTRP=${BTSTRP_X86}
 	fi
 
-	if use bootstrap; then
+	if ! use system-bootstrap; then
 		GCC="${WORKDIR}"/${BTSTRP}/bin/gcc
 	else
 		GCC=${ADA:-$(tc-getCC)}
@@ -78,10 +78,10 @@ src_prepare() {
 		GNATMAKE="${gnatpath}/${GNATMAKE}"
 	fi
 
-	if ! use bootstrap && [[ -z "$(type ${GNATMAKE} 2>/dev/null)" ]] ; then
+	if use system-bootstrap && [[ -z "$(type ${GNATMAKE} 2>/dev/null)" ]] ; then
 		eerror "You need a gcc compiler that provides the Ada Compiler:"
 		eerror "1) use gcc-config to select the right compiler or"
-		eerror "2) set the bootstrap use flag or"
+		eerror "2) disable the system-bootstrap use flag or"
 		eerror "3) set ADA to a working gcc ada compiler"
 		die "ada compiler not available"
 	fi
@@ -89,7 +89,7 @@ src_prepare() {
 	local bundledchost=""
 	use amd64 && local bundledchost="x86_64"
 	use x86 && local bundledchost="i686"
-	if use bootstrap; then
+	if ! use system-bootstrap; then
 		rm "${WORKDIR}"/${BTSTRP}/libexec/gcc/${bundledchost}-pc-linux-gnu/4.7.4/ld \
 			|| die
 		ln -s /usr/bin/$CHOST-ld \

dev-lang/gnat-gpl/metadata.xml

@@ -6,7 +6,6 @@
 	</maintainer>
 	<use>
 		<flag name="ada">Build the ADA language (GNAT) frontend</flag>
-		<flag name="bootstrap">Used to bootstrap gnat-gpl</flag>
 		<flag name="cet" restrict="&gt;=dev-lang/gnat-gpl-2021">Enable support for Intel Control Flow Enforcement Technology (CET)</flag>
 		<flag name="d">Enable support for the D programming language</flag>
 		<flag name="default-stack-clash-protection">Build packages with stack clash protection on by default</flag>
@@ -29,6 +28,7 @@
 		<flag name="pgo">Build GCC using Profile Guided Optimization (PGO)</flag>
 		<flag name="rust">Build support for the Rust language, installs gccrs.</flag>
 		<flag name="sanitize">Build support for various sanitizer functions (ASAN/TSAN/etc...)</flag>
+		<flag name="system-bootstrap">Bootstrap using installed Ada compiler</flag>
 		<flag name="systemtap">enable systemtap static probe points</flag>
 		<flag name="ssp">Build packages with stack smashing protector on by default</flag>
 		<flag name="vtv">Build support for virtual table verification (a C++ hardening feature)</flag>