dev-cpp/abseil-cpp: build with c++17

Build with C++17 for now to avoid ABI hell with std::*_ordering with
C++20. If abseil is built with a compiler that defaults to C++20, like
GCC 16, then reverse dependencies start to fail unless they're also
built with C++20. Just use C++17 to have the status quo for now to
unblock more GCC testing.

[sam: Wrote the commit message.]

Closes: https://bugs.gentoo.org/966846
Signed-off-by: Paul Zander <negril.nx+gentoo@gmail.com>
Signed-off-by: Sam James <sam@gentoo.org>

dev-cpp/abseil-cpp/abseil-cpp-20240722.1.ebuild

@@ -62,6 +62,7 @@ src_prepare() {
 
 multilib_src_configure() {
 	local mycmakeargs=(
+		-DCMAKE_CXX_STANDARD=17
 		-DABSL_ENABLE_INSTALL="yes"
 		-DABSL_USE_EXTERNAL_GOOGLETEST="yes"
 		-DABSL_PROPAGATE_CXX_STD="yes"

dev-cpp/abseil-cpp/abseil-cpp-20250127.1.ebuild

@@ -62,6 +62,7 @@ src_prepare() {
 
 multilib_src_configure() {
 	local mycmakeargs=(
+		-DCMAKE_CXX_STANDARD=17
 		-DABSL_ENABLE_INSTALL="yes"
 		-DABSL_USE_EXTERNAL_GOOGLETEST="yes"
 		-DABSL_PROPAGATE_CXX_STD="yes"

dev-cpp/abseil-cpp/abseil-cpp-20250512.1.ebuild

@@ -59,6 +59,7 @@ src_prepare() {
 
 multilib_src_configure() {
 	local mycmakeargs=(
+		-DCMAKE_CXX_STANDARD=17
 		-DABSL_ENABLE_INSTALL="yes"
 		-DABSL_USE_EXTERNAL_GOOGLETEST="yes"
 		-DABSL_PROPAGATE_CXX_STD="yes"

dev-cpp/abseil-cpp/abseil-cpp-20250814.1.ebuild

@@ -66,6 +66,7 @@ multilib_src_configure() {
 	append-cxxflags $(usex debug '-DDEBUG' '-DNDEBUG')
 
 	local mycmakeargs=(
+		-DCMAKE_CXX_STANDARD=17
 		-DABSL_ENABLE_INSTALL="yes"
 		-DABSL_USE_EXTERNAL_GOOGLETEST="yes"
 		-DABSL_PROPAGATE_CXX_STD="yes"