Makefile: do not compile rust/download_web with old toolchain

object crate beacume incompatible with Debian 10 toolchain (rust 1.41):

    error[E0658]: subslice patterns are unstable
       --> /root/.cargo/registry/src/github.com-1ecc6299db9ec823/object-0.23.0/src/read/mod.rs:162:41
        |
    162 |             [0x7f, b'E', b'L', b'F', 1, ..] => FileKind::Elf32,
        |                                         ^^
        |
        = note: for more information, see rust-lang/rust#62254

Makefile

@@ -96,11 +96,16 @@ else
 #   For more information about this error, try `rustc --explain E0210`.
 # Old versions of rustc (<=1.39) fail to build curl-0.4.34 because:
 #   error[E0658]: the `#[non_exhaustive]` attribute is an experimental feature
-#   ote: for more information, see https://github.com/rust-lang/rust/issues/44109
+#   note: for more information, see https://github.com/rust-lang/rust/issues/44109
+# Old versions of rustc (<=1.42) fail to build object-0.23.0 because:
+#   error[E0658]: subslice patterns are unstable
+#   note: for more information, see https://github.com/rust-lang/rust/issues/62254
 ifeq ($(call can-run,$(RUSTC) --version | grep '^rustc 1\.\(3[0-4]\)\.'),y)
 SUBDIRS_BLACKLIST += rust/asymkeyfind% rust/check_linux_pass% rust/download_web%
 else ifeq ($(call can-run,$(RUSTC) --version | grep '^rustc 1\.\(3[0-9]\)\.'),y)
 SUBDIRS_BLACKLIST += rust/check_linux_pass% rust/download_web%
+else ifeq ($(call can-run,$(RUSTC) --version | grep '^rustc 1\.\(4[0-1]\)\.'),y)
+SUBDIRS_BLACKLIST += rust/download_web%
 endif
 endif
 

machines/Dockerfile-alpine3.12

@@ -50,7 +50,7 @@ COPY . /shared/
 CMD ["/run_shared_test.sh"]
 
 # make list-nobuild:
-#    Global blacklist: latex%
+#    Global blacklist: latex% rust/download_web%
 #    In sub-directories:
 #       c: x86-read_64b_regs_in_32b_mode
 #       glossaries:

machines/Dockerfile-debian10-buster

@@ -62,7 +62,7 @@ COPY . /shared/
 CMD ["/run_shared_test.sh"]
 
 # make list-nobuild:
-#    Global blacklist: latex%
+#    Global blacklist: latex% rust/download_web%
 #    In sub-directories:
 #       c:
 #       glossaries:
@@ -76,7 +76,7 @@ CMD ["/run_shared_test.sh"]
 #       rust:
 #       verification:
 #    With gcc -m32:
-#       Global blacklist: latex%
+#       Global blacklist: latex% rust/download_web%
 #       In sub-directories:
 #          c: gmp_functions gtk_alpha_window
 #          glossaries:

machines/Dockerfile-fedora30

@@ -61,7 +61,7 @@ COPY . /shared/
 CMD ["/run_shared_test.sh"]
 
 # make list-nobuild:
-#    Global blacklist: latex%
+#    Global blacklist: latex% rust/download_web%
 #    In sub-directories:
 #       c:
 #       glossaries:
@@ -75,7 +75,7 @@ CMD ["/run_shared_test.sh"]
 #       rust:
 #       verification:
 #    With gcc -m32:
-#       Global blacklist: latex%
+#       Global blacklist: latex% rust/download_web%
 #       In sub-directories:
 #          c: gtk_alpha_window
 #          glossaries: