bintools,gcc: introduce mlibc support

In gcc, libsanitize is disabled because mlibc doesn't support
libsanitize yet but upstream is working on it. Patches needed for gcc to
support linux-mlibc targets are pulled from managarm's fork of gcc,
patches only needed by managarm are not applied.

pkgs/build-support/bintools-wrapper/default.nix

@@ -114,6 +114,7 @@ let
   # shell glob that ought to match it.
   dynamicLinker =
     /**/ if sharedLibraryLoader == null then ""
+    else if targetPlatform.libc == "mlibc"            then "${sharedLibraryLoader}/lib/ld.so"
     else if targetPlatform.libc == "musl"             then "${sharedLibraryLoader}/lib/ld-musl-*"
     else if targetPlatform.libc == "uclibc"           then "${sharedLibraryLoader}/lib/ld*-uClibc.so.1"
     else if (targetPlatform.libc == "bionic" && targetPlatform.is32bit) then "/system/bin/linker"

pkgs/development/compilers/gcc/common/configure-flags.nix

@@ -93,7 +93,7 @@ let
                           else if targetPlatform.isWindows then (threadsCross.model or "win32")
                           else "single"}"
       "--enable-nls"
-    ] ++ lib.optionals (targetPlatform.libc == "uclibc" || targetPlatform.libc == "musl") [
+    ] ++ lib.optionals (lib.elem targetPlatform.libc [ "mlibc" "musl" "uclibc" ]) [
       # libsanitizer requires netrom/netrom.h which is not
       # available in uclibc.
       "--disable-libsanitizer"
@@ -217,6 +217,7 @@ let
       # On Illumos/Solaris GNU as is preferred
       "--with-gnu-as" "--without-gnu-ld"
     ]
+    ++ lib.optional (targetPlatform.libc == "mlibc") "--disable-libsanitizer"
     ++ lib.optional (targetPlatform.libc == "musl")
       # musl at least, disable: https://git.buildroot.net/buildroot/commit/?id=873d4019f7fb00f6a80592224236b3ba7d657865
       "--disable-libmpx"

pkgs/development/compilers/gcc/patches/default.nix

@@ -137,6 +137,18 @@ in
   })
 ]
 
+## mlibc
+++ optionals (stdenv.targetPlatform.isMlibc && atLeast14) [
+  (fetchpatch {
+    url = "https://github.com/managarm/gcc/commit/092cb31af8ed12dbecc02327444f030a7c40c344.diff";
+    hash = "sha256-Ix95v0UxC73tfW2UliWiRgS0wC1wVUo5waM38qFlRFM=";
+  })
+  (fetchpatch {
+    url = "https://github.com/managarm/gcc/commit/b5cdfff8afc4a668e65541eec5b512d080116a43.diff";
+    hash = "sha256-0xbw/vRbUvsIIhXM8iyAxm2FWXDnYXblAJ1gFEgeOPg=";
+  })
+]
+
 ## Darwin
 
 # Fixes detection of Darwin on x86_64-darwin. Otherwise, GCC uses a deployment target of 10.5, which crashes ld64.