[xen staging] tools: Use -Og for debug builds when available

[patchbot@xxxxxxx]

commit 4abb20e321626c3d3cb0e922eac2048dc15d7c87
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Thu Feb 11 14:22:44 2021 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Fri Feb 19 17:10:33 2021 +0000

    tools: Use -Og for debug builds when available
    
    The recommended optimisation level for debugging is -Og, and is what tools
    such as gdb prefer.  In practice, it equates to -01 with a few specific
    optimisations turned off.
    
    abi-dumper in particular wants the libraries it inspects in this form.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Ian Jackson <iwj@xxxxxxxxxxxxxx>
    Release-Acked-by: Ian Jackson <iwj@xxxxxxxxxxxxxx>
---
 tools/Rules.mk | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/Rules.mk b/tools/Rules.mk
index f61da81f4a..2907ed2d39 100644
--- a/tools/Rules.mk
+++ b/tools/Rules.mk
@@ -106,8 +106,9 @@ endif
 CFLAGS_libxenlight += $(CFLAGS_libxenctrl)
 
 ifeq ($(debug),y)
-# Disable optimizations
-CFLAGS += -O0 -fno-omit-frame-pointer
+# Use -Og if available, -O0 otherwise
+dbg_opt_level := $(call cc-option,$(CC),-Og,-O0)
+CFLAGS += $(dbg_opt_level) -fno-omit-frame-pointer
 # But allow an override to -O0 in case Python enforces -D_FORTIFY_SOURCE=<n>.
 PY_CFLAGS += $(PY_NOOPT_CFLAGS)
 else
--
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