rust-common: Hack around LD_LIBRARY_PATH issues on centos7

When building cargo-native on centos7 with buildtools tarball installed,
we see failures:

/bin/sh: /lib64/libc.so.6: version `GLIBC_2.33' not found (required by /home/pokybuild/yocto-worker/reproducible-centos/build/build-st/tmp/work/x86_64-linux/cargo-native/1.54.0-r0/recipe-sysroot-native/usr/lib/libtinfo.so.5)

We also see this for libstd-rs once cargo-native is fixed.

The reason for this is that the wrapper script
cargo-native/1.54.0-r0/wrapper/target-rust-ccld has /bin/sh as it's
interpreter and cargo calls this with LD_LIBRARY_PATH set to include the
recipe-sysroot-native. The host /bin/sh links to libtinfo from the host
but it finds the version in the sysroot which needs a newer libc. This
results in the above error since the loader is an older libc and the two
are incompatible.

Our ccld wrapper calls gcc/ld which don't need the LD_LIBRARY_PATH
variable set. We can't patch this out the source since we're using
a prebuilt binary to generate a new cargo binary so this is impossible
to bootstrap.

Instead, put a binary wrapper into place which removes LD_LIBRARY_PATH
from the environment before calling the original wrapper (left in shell
as it is simpler to maintain).

(From OE-Core rev: 8feeeb7f76c6725e5226458c8f22999b67c52694)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/files/rust-ccld-wrapper.c

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2021 Richard Purdie
+ *
+ * SPDX-License-Identifier: GPL-2.0-only
+ */
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+/*
+ * Run the original script (argv[0] + ".real") with LD_LIBRARY_PATH unset
+ * This avoids issues where cargo is running a wrapper script using /bin/sh from the host
+ * which links to something which has an incompatible version in in recipe-sysroot-native
+ * such as libtinfo on centos 7.
+ */
+
+int main(int argc, char* argv[]) {
+    char *real = malloc(strlen(argv[0] + 5));
+    strcpy(real, argv[0]);
+    strcpy(real + strlen(argv[0]), ".real");
+    putenv("LD_LIBRARY_PATH=");
+    if(execv(real, argv) == -1) {
+        printf("Wrapper failed to execute, error: %s\n", strerror(errno));
+        return -1;
+    }
+}