fix: root-cause strtold — patch GCC <cstdlib> at prefix build time

Add explicit #include <stdlib.h> after #include_next <stdlib.h> in
GCC 13 cstdlib. This ensures ::strtold is declared before the
using-directives execute. Previously relibc's declaration was
not visible to the C++ wrapper.

Reverted unjustified ignores: qt6-sensors, kf6-ki18n, kf6-kidletime,
kf6-kwayland, redbear-greeter — per project policy: fix, don't ignore.

Also reverted kf6-ki18n to full build (stub removed).

config/redbear-full.toml

@@ -72,7 +72,7 @@ qtdeclarative = {}
 qtsvg = {}
 qtwayland = {}
 qt6-wayland-smoke = {}
-qt6-sensors = "ignore"
+qt6-sensors = {}
 
 # KF6 Frameworks — explicit real-build surface in alphabetical order
 # kirigami: blocked (Qt6 Wayland null+8 crash — NOT QML gate; headers/libs DO exist)
@@ -96,9 +96,9 @@ kf6-kdbusaddons = {}
 kf6-kdeclarative = {}
 kf6-kded6 = {}
 kf6-kguiaddons = {}
-kf6-ki18n = "ignore"
+kf6-ki18n = {}
 kf6-kiconthemes = {}
-kf6-kidletime = "ignore"
+kf6-kidletime = {}
 kf6-kitemmodels = {}
 kf6-kitemviews = {}
 kf6-kjobwidgets = {}
@@ -106,7 +106,7 @@ kf6-knotifications = {}
 kf6-kpackage = {}
 kf6-kservice = {}
 kf6-ktextwidgets = {}
-kf6-kwayland = "ignore"
+kf6-kwayland = {}
 kf6-kwidgetsaddons = {}
 kf6-kxmlgui = {}
 kf6-prison = {}
@@ -136,7 +136,7 @@ kwin = {}
 redbear-authd = {}
 redbear-session-launch = {}
 seatd = {}
-redbear-greeter = "ignore"
+redbear-greeter = {}
 pam-redbear = {}
 sddm = {}
 amdgpu = {}

mk/prefix.mk

@@ -113,14 +113,16 @@ else
 # libc.a copy in the toolchain is identical to the one just compiled.
 	cp -rf "$@/$(GNU_TARGET)/lib/"* "$(PREFIX)/gcc-install/$(GNU_TARGET)/lib/"
 	cp -rf "$@/$(GNU_TARGET)/include/"* "$(PREFIX)/gcc-install/$(GNU_TARGET)/include/"
-# Fix GCC 13 <cstdlib> — relibc declares but doesn't implement strtold (long double).
-# GCC was built with _GLIBCXX_USE_C99_STDLIB=1 but relibc lacks the symbol.
-# Remove 'using ::strtold' from the C++ stdlib header to prevent compile errors.
-# Also remove stold() from basic_string.h which references std::strtold.
-	export _GCC_CSTDLIB="$(PREFIX)/gcc-install/$(GNU_TARGET)/include/c++"/*/cstdlib; \
-	sed -i '/using ::strtold;/d; /using ::__gnu_cxx::strtold;/d' $$_GCC_CSTDLIB 2>/dev/null || true; \
-	STRHDR="$(PREFIX)/gcc-install/$(GNU_TARGET)/include/c++"/*/bits/basic_string.h; \
-	sed -i '/inline long double/,/^#endif \/\/ _GLIBCXX_USE_C99_STDLIB/{ /stold(/,/^#endif/d; }' $$STRHDR 2>/dev/null || true
+# Relibc declares strtold in stdlib.h, but GCC <cstdlib>'s include_next
+# may not find it before processing 'using ::strtold'.  Prepend an
+# explicit #include <stdlib.h> to the C++ header so ::strtold is in
+# scope by the time the using-directives execute.  The edit must
+# happen AFTER the #include_next <stdlib.h> line (which brings in
+# most of the C declarations) but BEFORE the first using-directive.
+	for _cstdlib in "$(PREFIX)/gcc-install/$(GNU_TARGET)/include/c++"/*/cstdlib; do \
+		[ -f "$$_cstdlib" ] || continue; \
+		sed -i '/^#include_next <stdlib.h>$$/a\\n// Red Bear: relibc declares strtold via cbindgen trailer.\n// The explicit include ensures ::strtold is visible when the\n// C++ wrapper processes its using-directives below.\n#include <stdlib.h>' "$$_cstdlib"; \
+	done
 # Propagate fresh relibc artifacts to the redoxer toolchain at
 # ~/.redoxer/<target>/toolchain/.  The redoxer ships its own sysroot
 # snapshot from initial setup; without this sync the GCC driver inside