Include rodata subsections in FIPS-shared build.

Sometimes the linker will generate rodata subsections even if we don't
have -fdata-sections enabled. That's ok, so include them in the FIPS
module. The other subsections continue to be discarded to ensure that
unexpected sections don't appear and escape the module.

Bug: b/142971559

Change-Id: Icebcf40bd3d0e63f20456e44f6c2564f4316b561
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/43324
Commit-Queue: Adam Langley <alangley@gmail.com>
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: David Benjamin <davidben@google.com>

crypto/fipsmodule/fips_shared.lds

@@ -8,18 +8,17 @@ SECTIONS
   .rodata : {
     BORINGSSL_bcm_rodata_start = .;
     *(.rodata)
+    *(.rodata.*)
     BORINGSSL_bcm_rodata_end = .;
   }
 
   /DISCARD/ : {
+    /* These sections shouldn't exist. In order to catch any slip-ups, direct
+     * the linker to discard them. */
     *(.rela.dyn)
     *(.data)
     *(.rel.ro)
     *(*.text.*)
     *(*.data.*)
-
-    /* This should be included to catch any unexpected rodata subsections, but
-       it crashes the linker!
-    *(*.rodata.*) */
   }
 }