ci: Ignore non-rust warnings

This should make it easier for us to ignore warnings from outside the
rust front end, and therefore make it easier for us to pull from
upstream.

ChangeLog:

	* .github/alpine_32bit_log_warnings: Remove lines.
	* .github/glibcxx_ubuntu64b_log_expected_warnings: Likewise.
	* .github/log_expected_warnings: Likewise.
	* .github/workflows/ccpp.yml: Filter out non-rust warnings.
	* .github/workflows/ccpp32alpine.yml: Likewise and remove
	redundant command.
	* .github/safe-grep: New shell script.

Signed-off-by: Owen Avery <powerboat9.gamer@gmail.com>

Author: powerboat9

.github/alpine_32bit_log_warnings

@@ -0,0 +1,11 @@
+#!/bin/sh
+# grep exits with 1 if it doesn't match any lines
+# this script wraps grep, mapping exits codes 1->0, x->x
+
+grep "$@"
+EXIT_CODE="$?"
+if [ x$EXIT_CODE = x1 ]; then
+  exit 0
+else
+  exit $EXIT_CODE
+fi

.github/glibcxx_ubuntu64b_log_expected_warnings

@@ -68,7 +68,7 @@ jobs:
     - name: Check for new warnings
       run: |
            cd gccrs-build
-           < log grep 'warning: ' | sort > log_warnings
+           < log grep 'warning: ' | grep rust | sort > log_warnings
            if diff -U0 ../.github/log_expected_warnings log_warnings; then
                :
            else
@@ -153,7 +153,7 @@ jobs:
     - name: Check for new warnings
       run: |
            cd gccrs-build
-           < log grep 'warning: ' | sort > log_warnings
+           < log grep 'warning: ' | grep rust | sort > log_warnings
            if diff -U0 ../.github/glibcxx_ubuntu64b_log_expected_warnings log_warnings; then
                :
            else
@@ -237,7 +237,7 @@ jobs:
     - name: Check for new warnings
       run: |
            cd gccrs-build
-           < log grep 'warning: ' | sort > log_warnings
+           < log grep 'warning: ' | grep rust | sort > log_warnings
            if diff -U0 ../.github/log_expected_warnings log_warnings; then
                :
            else

.github/log_expected_warnings

@@ -80,7 +80,8 @@ jobs:
     - name: Produce warning logs
       run: |
            cd gccrs-build
-           < log grep 'warning: ' | sort > log_warnings
+           # grep exits with 1 if it doesn't find at least one match
+           < log grep 'warning: ' | ../.github/safe-grep rust | sort > log_warnings
            cat log_warnings
       shell: alpine.sh {0}
     - name: Archive warnings logs
@@ -92,7 +93,6 @@ jobs:
     - name: Check for new warnings
       run: |
            cd gccrs-build
-           < log grep 'warning: ' | sort > log_warnings
            if diff -U0 ../.github/alpine_32bit_log_warnings log_warnings; then
                :
            else