rrpage: use Linux vDSO soname

AddressSanitizer complains if it isn't the first shared object in the
link map besides the vDSO. It checks for the vDSO by testing whether
the DT_SONAME of the object starts with 'linux-'. With the
introduction of librrpage, this check no longer passes and causes
ASan-instrumented programs to abort when being recorded by rr.

This patch alters the linker arguments used for producing the
librrpage dummy vDSO such that its SONAME is 'linux-vdso.so.1'.

CMakeLists.txt

@@ -342,7 +342,8 @@ foreach(file ${RR_PAGE_FILES})
   set_source_files_properties("${CMAKE_SOURCE_DIR}/src/preload/${file}"
                               PROPERTIES COMPILE_FLAGS ${PRELOAD_COMPILE_FLAGS})
 endforeach(file)
-set_target_properties(rrpage PROPERTIES LINK_FLAGS "-Wl,-T -Wl,${CMAKE_SOURCE_DIR}/src/preload/rr_page.ld -nostartfiles -nostdlib -Wl,-z,max-page-size=0x1000 ${LINKER_FLAGS}")
+set_target_properties(rrpage PROPERTIES NO_SONAME ON)
+set_target_properties(rrpage PROPERTIES LINK_FLAGS "-Wl,-T -Wl,${CMAKE_SOURCE_DIR}/src/preload/rr_page.ld -nostartfiles -nostdlib -Wl,-z,max-page-size=0x1000 -Wl,-soname,linux-vdso.so.1 ${LINKER_FLAGS}")
 set_target_properties(rrpage PROPERTIES LINK_DEPENDS ${CMAKE_SOURCE_DIR}/src/preload/rr_page.ld)
 # CMake seems to have trouble generating the link line without this
 set_target_properties(rrpage PROPERTIES LINKER_LANGUAGE C)
@@ -664,7 +665,8 @@ if(rr_32BIT AND rr_64BIT)
                                 PROPERTIES COMPILE_FLAGS "-m32 ${PRELOAD_COMPILE_FLAGS}")
   endforeach(file)
 
-  set_target_properties(rrpage_32 PROPERTIES LINK_FLAGS "-m32 -Wl,-T -Wl,${CMAKE_SOURCE_DIR}/src/preload/rr_page.ld -nostartfiles -nostdlib ${LINKER_FLAGS}")
+  set_target_properties(rrpage_32 PROPERTIES NO_SONAME ON)
+  set_target_properties(rrpage_32 PROPERTIES LINK_FLAGS "-m32 -Wl,-T -Wl,${CMAKE_SOURCE_DIR}/src/preload/rr_page.ld -nostartfiles -nostdlib -Wl,-soname,linux-vdso.so.1 ${LINKER_FLAGS}")
   set_target_properties(rrpage_32 PROPERTIES LINK_DEPENDS ${CMAKE_SOURCE_DIR}/src/preload/rr_page.ld)
   set_target_properties(rrpage_32 PROPERTIES LINKER_LANGUAGE C)