let tracepoint info section inherit section group

Summary:
Originally submitted by github user aliher1911 https://github.com/aliher1911 in: https://github.com/aliher1911. However, the files were moved around and the importer cannot import this PR.

Original description:
> When section group is inherited from the function where tracepoint is defined, tracepoint definition could be discarded by linker together with function correctly. Otherwise tracepoint would reference discarded section and cause linker to fail as in #1395.

Closes: #1396.
Fixes: #1395.
Fixes: facebook/fbthrift#384.

Reviewed By: Orvid

Differential Revision: D62073054

fbshipit-source-id: d75de3f3c37d3110ae5bc88cd0b6c3de5ebe331f

folly/tracing/StaticTracepoint-ELF.h

@@ -131,7 +131,7 @@
 // Structure of note section for the probe.
 #define FOLLY_SDT_NOTE_CONTENT(provider, name, has_semaphore, arg_template)    \
   FOLLY_SDT_ASM_1(990: FOLLY_SDT_NOP)                                          \
-  FOLLY_SDT_ASM_3(     .pushsection .note.stapsdt,"","note")                   \
+  FOLLY_SDT_ASM_3(     .pushsection .note.stapsdt,"?","note")                  \
   FOLLY_SDT_ASM_1(     .balign 4)                                              \
   FOLLY_SDT_ASM_3(     .4byte 992f-991f, 994f-993f, FOLLY_SDT_NOTE_TYPE)       \
   FOLLY_SDT_ASM_1(991: .asciz FOLLY_SDT_NOTE_NAME)                             \