rustc: host platform libraries missing when building cross-compiler

[lopsided98]

With the update to 1.48, rustc is missing some host platform libraries when built as a cross-compiler. Most notably, std is missing which causes cross-compiled packages with build.rs scripts to fail with the following error:

  configuring
  Running cd .
  Building build.rs (arrayvec)
  Running rustc --crate-name build_script_build build.rs --crate-type bin -C opt-level=3 -C codegen-units=2 --edition 2015 --out-dir target/build/arrayvec --emit=dep-info,link -L dependency=target/buildDeps --cap-lints allow --color always
  error[E0463]: can't find crate for `std`
  
  error: aborting due to previous error
  
  For more information about this error, try `rustc --explain E0463`.

The native (host == target) compiler is not affected. The diff between the native and cross lib/rustlib/x86_64-unknown-linux-gnu/lib directory is as follows:

@@ -1,2 +0,0 @@
-libaddr2line-fd0a11781cac1ae6.rlib
-libadler-37cb53a92bfc5f37.rlib
@@ -4 +1,0 @@
-liballoc-a19fe38287aa7b44.rlib
@@ -15 +11,0 @@
-libcfg_if-37ec6e35a57c4724.rlib
@@ -22,2 +17,0 @@
-libcompiler_builtins-12b2430788b08c11.rlib
-libcore-589330c3ebfd1b26.rlib
@@ -37 +30,0 @@
-libgetopts-91d871b325b54499.rlib
@@ -39,2 +31,0 @@
-libgimli-f906aedc6bbb423e.rlib
-libhashbrown-7db2809e2d4e5810.rlib
@@ -49 +39,0 @@
-liblibc-efefef0138314610.rlib
@@ -61 +50,0 @@
-libminiz_oxide-8013efd62c3d03e3.rlib
@@ -65 +53,0 @@
-libobject-737dda8c0fec8d45.rlib
@@ -67,2 +54,0 @@
-libpanic_abort-e5b513f46ea93372.rlib
-libpanic_unwind-893763619bc2225f.rlib
@@ -77,2 +62,0 @@
-libproc_macro-1bad6b8419dd53b0.rlib
-libprofiler_builtins-10268f4ed46fc3a0.rlib
@@ -101 +84,0 @@
-librustc_demangle-acce1e25cb491fdd.rlib
@@ -138,3 +120,0 @@
-librustc_std_workspace_alloc-7a2650f8bf27257e.rlib
-librustc_std_workspace_core-2f7b014fd614d1d2.rlib
-librustc_std_workspace_std-0b77cfa14afcf570.rlib
@@ -159,2 +138,0 @@
-libstd-1f9f29bebaffd5df.rlib
-libstd-1f9f29bebaffd5df.so
@@ -162 +139,0 @@
-libterm-d21a5a5896130801.rlib
@@ -165,2 +141,0 @@
-libtest-c2439ed74999a4f0.rlib
-libtest-c2439ed74999a4f0.so
@@ -182 +156,0 @@
-libunicode_width-d9340def170ced68.rlib
@@ -184 +157,0 @@
-libunwind-19130fdd94e76f94.rlib

This seems like an upstream regression. Interestingly, the list of missing libraries exactly matches the list of libraries installed in lib/rustlib/<target>/lib.

cc @Ericson2314 @petabyteboy

[lopsided98]

rust-lang/rust@4de836e looks kind of suspicious.

[lopsided98]

Or actually rust-lang/rust#76415 looks like it would explain the issue. I think we need to add the host platform to targets as well.

[Ericson2314]

That makes sense to me and sounds like a good solution.