[PATCH 14/27] gdb/testsuite: Support text_segment on windows-msvc via /BASE

The gdb_compile text_segment option asks the linker to place the image
at a specific base address.  It dispatches to the right linker flag by
probing which one the linker accepts:

 -Ttext-segment => GNU ld
 --image-base   => LLVM's lld
 -Ttext         => gold

None of those are accepted by lld-link, the linker clang drives on a
windows-msvc target, so gdb_compile errors out with "Don't know how to
handle text_segment option."

Add a fourth probe case using lld-link's /BASE switch, gated on a new
linker_supports_base_flag probe that mirrors the existing ones.  /BASE
sets the preferred image base the same way GNU ld's --image-base does.

Change-Id: I84d5a3de6d755a3794abb7358b16de5e516ddefa
---
 gdb/testsuite/lib/gdb.exp | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
index fcef2022a43..bece5b6044d 100644
--- a/gdb/testsuite/lib/gdb.exp
+++ b/gdb/testsuite/lib/gdb.exp
@@ -6853,6 +6853,9 @@ proc gdb_compile {source dest type options} {
 	    } elseif { [linker_supports_image_base_flag] } {
 		# For GNU ld on PE and for LLVM's lld.
 		lappend new_options "ldflags=-Wl,--image-base=$addr"
+	    } elseif { [linker_supports_base_flag] } {
+		# For lld-link (MSVC link.exe compatible mode).
+		lappend new_options "ldflags=-Wl,/BASE:$addr"
 	    } elseif { [linker_supports_Ttext_flag] } {
 		# For old GNU gold versions.
 		lappend new_options "ldflags=-Wl,-Ttext=$addr"
@@ -11457,6 +11460,15 @@ gdb_caching_proc linker_supports_image_base_flag {} {
     return [gdb_simple_compile $me $src executable $flags]
 }
 
+# Return 1 if linker supports /BASE (lld-link / MSVC link.exe),
+# otherwise 0.
+gdb_caching_proc linker_supports_base_flag {} {
+    set me "linker_supports_base_flag"
+    set flags ldflags=[quote_for_host -Wl,/BASE:0x7000000]
+    set src { int main() { return 0; } }
+    return [gdb_simple_compile $me $src executable $flags]
+}
+
 # Return 1 if the linker is lld-link which can embed our application
 # manifest by itself, otherwise 0.  Probes the exact flag combination
 # gdb_compile uses.
-- 
2.54.0