diff -Nru rustc-1.40.0+dfsg1/debian/architecture.mk rustc-1.40.0+dfsg1/debian/architecture.mk
--- rustc-1.40.0+dfsg1/debian/architecture.mk	2020-01-04 04:16:35.000000000 +0000
+++ rustc-1.40.0+dfsg1/debian/architecture.mk	2020-01-11 11:16:08.000000000 +0000
@@ -3,10 +3,7 @@
 include /usr/share/dpkg/architecture.mk
 
 rust_cpu = $(subst i586,i686,\
-$(if $(findstring -riscv64-,-$(2)-),$(subst riscv64,riscv64gc,$(1)),\
-$(if $(findstring -armhf-,-$(2)-),$(subst arm,armv7,$(1)),\
-$(if $(findstring -armel-,-$(2)-),$(subst arm,armv5te,$(1)),\
-$(1)))))
+$(if $(findstring -riscv64-,-$(2)-),$(subst riscv64,riscv64gc,$(1)),$(1)))
 rust_type_setvar = $(1)_RUST_TYPE ?= $(call rust_cpu,$($(1)_GNU_CPU),$($(1)_ARCH))-unknown-$($(1)_GNU_SYSTEM)
 
 $(foreach machine,BUILD HOST TARGET,\
@@ -16,3 +13,5 @@
 ifeq ($(DEB_TARGET_RUST_TYPE),-unknown-)
   DEB_TARGET_RUST_TYPE = $(DEB_HOST_RUST_TYPE)
 endif
+
+DEB_BUILD_RUST_TYPE = $(shell dpkg -L rustc | grep '/usr/lib/rustlib/' | head -n 1 | cut -d '/' -f 5)
diff -Nru rustc-1.40.0+dfsg1/debian/changelog rustc-1.40.0+dfsg1/debian/changelog
--- rustc-1.40.0+dfsg1/debian/changelog	2020-01-05 13:35:46.000000000 +0000
+++ rustc-1.40.0+dfsg1/debian/changelog	2020-01-11 11:16:08.000000000 +0000
@@ -1,3 +1,14 @@
+rustc (1.40.0+dfsg1-5+rpi1) bullseye-staging; urgency=medium
+
+  [changes brought forward from 1.15.1+dfsg1-1~exp3+rpi1 by Peter Michael Green <plugwash@raspbian.org> at Wed, 15 Mar 2017 10:16:18 +0000]
+  * Build for armv6.
+  [changes introduced in 1.18.0+dfsg1-4+rpi1 by Peter Michael Green]
+  * Disable testsuite.
+  [changes introduced in 1.37.0+dfsg1-1+rpi1 by Peter Michael Green]
+  * Set DEB_BUILD_RUST_TYPE based on the compiler that is actually installed.
+
+ -- Raspbian forward porter <root@raspbian.org>  Sat, 11 Jan 2020 11:16:08 +0000
+
 rustc (1.40.0+dfsg1-5) unstable; urgency=medium
 
   * More python 2 -> 3 fixes.
diff -Nru rustc-1.40.0+dfsg1/debian/rules rustc-1.40.0+dfsg1/debian/rules
--- rustc-1.40.0+dfsg1/debian/rules	2020-01-05 13:33:55.000000000 +0000
+++ rustc-1.40.0+dfsg1/debian/rules	2020-01-11 11:16:08.000000000 +0000
@@ -240,7 +240,7 @@
 		test "$$(stat -c %s "$$x")" -lt 6000000; \
 	done
 ifeq (, $(filter nocheck,$(DEB_BUILD_PROFILES)))
-ifeq (, $(filter nocheck,$(DEB_BUILD_OPTIONS)))
+ifeq (testsuitedisabled, $(filter nocheck,$(DEB_BUILD_OPTIONS)))
 	{ $(RUSTBUILD_TEST) $(RUSTBUILD_FLAGS) $(RUSTBUILD_TEST_FLAGS); echo $$?; } | tee -a $(TEST_LOG)
 	# test that the log has at least 1 pass, to prevent e.g. #57709
 	grep -l "^test .* \.\.\. ok$$" $(TEST_LOG)