gcc: fix cross compilation to musl32

pkgs/development/compilers/gcc/7/default.nix

@@ -73,7 +73,7 @@ let majorVersion = "7";
       ++ optional langFortran ../gfortran-driving.patch
       ++ optional (targetPlatform.libc == "musl" && targetPlatform.isPower) ../ppc-musl.patch
       ++ optional (targetPlatform.libc == "musl" && targetPlatform.isx86_32) (fetchpatch {
-        url = "https://git.alpinelinux.org/aports/plain/main/gcc/gcc-6.1-musl-libssp.patch";
+        url = "https://git.alpinelinux.org/aports/plain/main/gcc/gcc-6.1-musl-libssp.patch?id=5e4b96e23871ee28ef593b439f8c07ca7c7eb5bb";
         sha256 = "1jf1ciz4gr49lwyh8knfhw6l5gvfkwzjy90m7qiwkcbsf4a3fqn2";
       })
       ++ optional (targetPlatform.libc == "musl") ../libgomp-dont-force-initial-exec.patch

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

@@ -94,9 +94,6 @@ let
       # In uclibc cases, libgomp needs an additional '-ldl'
       # and as I don't know how to pass it, I disable libgomp.
       "--disable-libgomp"
-    ] ++ lib.optionals (targetPlatform.libc == "musl") [
-      # musl at least, disable: https://git.buildroot.net/buildroot/commit/?id=873d4019f7fb00f6a80592224236b3ba7d657865
-      "--disable-libmpx"
     ] ++ lib.optional (targetPlatform.libc == "newlib") "--with-newlib"
       ++ lib.optional (targetPlatform.libc == "avrlibc") "--with-avrlibc"
     );
@@ -181,6 +178,9 @@ let
       # On Illumos/Solaris GNU as is preferred
       "--with-gnu-as" "--without-gnu-ld"
     ]
+    ++ lib.optional (targetPlatform.libc == "musl")
+      # musl at least, disable: https://git.buildroot.net/buildroot/commit/?id=873d4019f7fb00f6a80592224236b3ba7d657865
+      "--disable-libmpx"
     ++ lib.optionals (targetPlatform == hostPlatform && targetPlatform.libc == "musl") [
       "--disable-libsanitizer"
       "--disable-symvers"

pkgs/top-level/all-packages.nix

@@ -9827,6 +9827,9 @@ in
     libcCross = if stdenv.targetPlatform != stdenv.buildPlatform then libcCross else null;
     threadsCross = if stdenv.targetPlatform != stdenv.buildPlatform then threadsCross else null;
 
+    # gcc 10 is too strict to cross compile gcc <= 8
+    stdenv = if (stdenv.targetPlatform != stdenv.buildPlatform) && stdenv.cc.isGNU then gcc7Stdenv else stdenv;
+
     isl = if stdenv.isDarwin
             then null
           else if stdenv.targetPlatform.isRedox
@@ -9843,6 +9846,9 @@ in
     libcCross = if stdenv.targetPlatform != stdenv.buildPlatform then libcCross else null;
     threadsCross = if stdenv.targetPlatform != stdenv.buildPlatform then threadsCross else null;
 
+    # gcc 10 is too strict to cross compile gcc <= 8
+    stdenv = if (stdenv.targetPlatform != stdenv.buildPlatform) && stdenv.cc.isGNU then gcc7Stdenv else stdenv;
+
     isl = if !stdenv.isDarwin then isl_0_17 else null;
   }));
 
@@ -9855,6 +9861,9 @@ in
     libcCross = if stdenv.targetPlatform != stdenv.buildPlatform then libcCross else null;
     threadsCross = if stdenv.targetPlatform != stdenv.buildPlatform then threadsCross else null;
 
+    # gcc 10 is too strict to cross compile gcc <= 8
+    stdenv = if (stdenv.targetPlatform != stdenv.buildPlatform) && stdenv.cc.isGNU then gcc7Stdenv else stdenv;
+
     isl = if !stdenv.isDarwin then isl_0_17 else null;
   }));