nixos/installer/cd-dvd: use EFI/BOOT and EFI/BOOT/BOOT$ARCH.EFI rather than lowercase

Reported in https://discourse.nixos.org/t/nix-iso-unable-to-boot-in-uefi-mode-but-other-distros-can/16473/24

There seems to be weird situations with casing and FAT8.3 filenames, UEFI firmwares and what not.
To increase our compatibility, let's ensure we have the critical stuff (the bootable) in uppercase.

Signed-off-by: Raito Bezarius <masterancpp@gmail.com>

nixos/modules/installer/cd-dvd/iso-image.nix

@@ -159,7 +159,7 @@ let
     if refindBinary != null then
       ''
       # Adds rEFInd to the ISO.
-      cp -v ${pkgs.refind}/share/refind/${refindBinary} $out/EFI/boot/
+      cp -v ${pkgs.refind}/share/refind/${refindBinary} $out/EFI/BOOT/
       ''
     else
       "# No refind for ${targetArch}"
@@ -210,11 +210,11 @@ let
     ${ # When there is a theme configured, use it, otherwise use the background image.
     if config.isoImage.grubTheme != null then ''
       # Sets theme.
-      set theme=(\$root)/EFI/boot/grub-theme/theme.txt
+      set theme=(\$root)/EFI/BOOT/grub-theme/theme.txt
       # Load theme fonts
-      $(find ${config.isoImage.grubTheme} -iname '*.pf2' -printf "loadfont (\$root)/EFI/boot/grub-theme/%P\n")
+      $(find ${config.isoImage.grubTheme} -iname '*.pf2' -printf "loadfont (\$root)/EFI/BOOT/grub-theme/%P\n")
     '' else ''
-      if background_image (\$root)/EFI/boot/efi-background.png; then
+      if background_image (\$root)/EFI/BOOT/efi-background.png; then
         # Black background means transparent background when there
         # is a background image set... This seems undocumented :(
         set color_normal=black/black
@@ -235,7 +235,7 @@ let
     nativeBuildInputs = [ pkgs.buildPackages.grub2_efi ];
     strictDeps = true;
   } ''
-    mkdir -p $out/EFI/boot/
+    mkdir -p $out/EFI/BOOT
 
     # Add a marker so GRUB can find the filesystem.
     touch $out/EFI/nixos-installer-image
@@ -309,13 +309,13 @@ let
     # probe for devices, even with --skip-fs-probe.
     grub-mkimage \
       --directory=${grubPkgs.grub2_efi}/lib/grub/${grubPkgs.grub2_efi.grubTarget} \
-      -o $out/EFI/boot/boot${targetArch}.efi \
+      -o $out/EFI/BOOT/BOOT${lib.toUpper targetArch}.EFI \
-      -p /EFI/boot \
+      -p /EFI/BOOT \
       -O ${grubPkgs.grub2_efi.grubTarget} \
       ''${MODULES[@]}
-    cp ${grubPkgs.grub2_efi}/share/grub/unicode.pf2 $out/EFI/boot/
+    cp ${grubPkgs.grub2_efi}/share/grub/unicode.pf2 $out/EFI/BOOT/
 
-    cat <<EOF > $out/EFI/boot/grub.cfg
+    cat <<EOF > $out/EFI/BOOT/grub.cfg
 
     set textmode=${lib.boolToString (config.isoImage.forceTextMode)}
     set timeout=${toString grubEfiTimeout}
@@ -331,12 +331,12 @@ let
     ${grubMenuCfg}
 
     hiddenentry 'Text mode' --hotkey 't' {
-      loadfont (\$root)/EFI/boot/unicode.pf2
+      loadfont (\$root)/EFI/BOOT/unicode.pf2
       set textmode=true
       terminal_output console
     }
     hiddenentry 'GUI mode' --hotkey 'g' {
-      $(find ${config.isoImage.grubTheme} -iname '*.pf2' -printf "loadfont (\$root)/EFI/boot/grub-theme/%P\n")
+      $(find ${config.isoImage.grubTheme} -iname '*.pf2' -printf "loadfont (\$root)/EFI/BOOT/grub-theme/%P\n")
       set textmode=false
       terminal_output gfxterm
     }
@@ -411,7 +411,7 @@ let
         # Force root to be the FAT partition
         # Otherwise it breaks rEFInd's boot
         search --set=root --no-floppy --fs-uuid 1234-5678
-        chainloader (\$root)/EFI/boot/${refindBinary}
+        chainloader (\$root)/EFI/BOOT/${refindBinary}
       }
     fi
     ''}
@@ -427,7 +427,7 @@ let
     }
     EOF
 
-    grub-script-check $out/EFI/boot/grub.cfg
+    grub-script-check $out/EFI/BOOT/grub.cfg
 
     ${refind}
   '';
@@ -440,8 +440,8 @@ let
     #   dates (cp -p, touch, mcopy -m, faketime for label), IDs (mkfs.vfat -i)
     ''
       mkdir ./contents && cd ./contents
-      mkdir -p ./EFI/boot
+      mkdir -p ./EFI/BOOT
-      cp -rp "${efiDir}"/EFI/boot/{grub.cfg,*.efi} ./EFI/boot
+      cp -rp "${efiDir}"/EFI/BOOT/{grub.cfg,*.EFI,*.efi} ./EFI/BOOT
 
       # Rewrite dates for everything in the FS
       find . -exec touch --date=2000-01-01 {} +
@@ -836,11 +836,11 @@ in
         { source = "${efiDir}/EFI";
           target = "/EFI";
         }
-        { source = (pkgs.writeTextDir "grub/loopback.cfg" "source /EFI/boot/grub.cfg") + "/grub";
+        { source = (pkgs.writeTextDir "grub/loopback.cfg" "source /EFI/BOOT/grub.cfg") + "/grub";
           target = "/boot/grub";
         }
         { source = config.isoImage.efiSplashImage;
-          target = "/EFI/boot/efi-background.png";
+          target = "/EFI/BOOT/efi-background.png";
         }
       ] ++ lib.optionals (config.boot.loader.grub.memtest86.enable && config.isoImage.makeBiosBootable) [
         { source = "${pkgs.memtest86plus}/memtest.bin";
@@ -848,7 +848,7 @@ in
         }
       ] ++ lib.optionals (config.isoImage.grubTheme != null) [
         { source = config.isoImage.grubTheme;
-          target = "/EFI/boot/grub-theme";
+          target = "/EFI/BOOT/grub-theme";
         }
       ];