bfd: Close the file descriptor if there is no archive fd

Close the file descriptor if there is no archive plugin file descriptor
to avoid running out of file descriptors on thin archives with many
archive members.

bfd/

	PR ld/28138
	* plugin.c (bfd_plugin_close_file_descriptor): Close the file
	descriptor there is no archive plugin file descriptor.

ld/

	PR ld/28138
	* testsuite/ld-plugin/lto.exp: Run ld/28138 tests.
	* testsuite/ld-plugin/pr28138.c: New file.
	* testsuite/ld-plugin/pr28138-1.c: Likewise.
	* testsuite/ld-plugin/pr28138-2.c: Likewise.
	* testsuite/ld-plugin/pr28138-3.c: Likewise.
	* testsuite/ld-plugin/pr28138-4.c: Likewise.
	* testsuite/ld-plugin/pr28138-5.c: Likewise.
	* testsuite/ld-plugin/pr28138-6.c: Likewise.
	* testsuite/ld-plugin/pr28138-7.c: Likewise.

bfd/plugin.c

@@ -291,6 +291,14 @@ bfd_plugin_close_file_descriptor (bfd *abfd, int fd)
 	     && !bfd_is_thin_archive (abfd->my_archive))
 	abfd = abfd->my_archive;
 
+      /* Close the file descriptor if there is no archive plugin file
+	 descriptor.  */
+      if (abfd->archive_plugin_fd == -1)
+	{
+	  close (fd);
+	  return;
+	}
+
       abfd->archive_plugin_fd_open_count--;
       /* Dup the archive plugin file descriptor for later use, which
 	 will be closed by _bfd_archive_close_and_cleanup.  */

ld/testsuite/ld-plugin/lto.exp

@@ -930,4 +930,34 @@ if { [check_lto_fat_available] } {
     }
 }
 
+run_cc_link_tests [list \
+    [list \
+	"Build pr28138.a" \
+	"-T" "" \
+	{pr28138-1.c pr28138-2.c pr28138-3.c pr28138-4.c pr28138-5.c \
+	 pr28138-6.c pr28138-7.c} {} "pr28138.a" \
+    ] \
+    [list \
+	"Build pr28138.o" \
+	"" "" \
+	{pr28138.c} {} \
+    ] \
+]
+
+set exec_output [run_host_cmd "sh" \
+			      "-c \"ulimit -n 20; \
+			      $CC -Btmpdir/ld -o tmpdir/pr28138 \
+			      tmpdir/pr28138.o tmpdir/pr28138.a\""]
+set exec_output [prune_warnings $exec_output]
+if [string match "" $exec_output] then {
+    set exec_output [run_host_cmd "tmpdir/pr28138" ""]
+    if [string match "PASS" $exec_output] then {
+	pass "PR ld/28138"
+    } else {
+	fail "PR ld/28138"
+    }
+} else {
+    fail "PR ld/28138"
+}
+
 restore_notify

ld/testsuite/ld-plugin/pr28138-1.c

@@ -0,0 +1,6 @@
+extern int a0(void);
+int
+a1(void)
+{
+  return 1 + a0();
+}

ld/testsuite/ld-plugin/pr28138-2.c

@@ -0,0 +1,6 @@
+extern int a1(void);
+int
+a2(void)
+{
+  return 1 + a1();
+}

ld/testsuite/ld-plugin/pr28138-3.c

@@ -0,0 +1,6 @@
+extern int a2(void);
+int
+a3(void)
+{
+  return 1 + a2();
+}

ld/testsuite/ld-plugin/pr28138-4.c

@@ -0,0 +1,6 @@
+extern int a3(void);
+int
+a4(void)
+{
+  return 1 + a3();
+}

ld/testsuite/ld-plugin/pr28138-5.c

@@ -0,0 +1,6 @@
+extern int a4(void);
+int
+a5(void)
+{
+  return 1 + a4();
+}

ld/testsuite/ld-plugin/pr28138-6.c

@@ -0,0 +1,6 @@
+extern int a5(void);
+int
+a6(void)
+{
+  return 1 + a5();
+}

ld/testsuite/ld-plugin/pr28138-7.c

@@ -0,0 +1,6 @@
+extern int a6(void);
+int
+a7(void)
+{
+  return 1 + a6();
+}

ld/testsuite/ld-plugin/pr28138.c

@@ -0,0 +1,20 @@
+#include <stdio.h>
+
+extern int a7(void);
+
+int
+a0(void)
+{
+  return 0;
+}
+
+int
+main()
+{
+  if (a7() == 7)
+    {
+      printf ("PASS\n");
+      return 0;
+    }
+  return 1;
+}