[NFC][flang] Fix driver linker tests on Windows (#116667)

Author: DavidTruby

flang/test/Driver/dynamic-linker.f90

@@ -17,7 +17,7 @@
 ! GNU-LINKER-OPTIONS-SAME: "-static"
 ! GNU-LINKER-OPTIONS-SAME: "-rpath" "/path/to/dir"
 
-! RDYNAMIC-LINKER-OPTION: "{{.*}}ld"
+! RDYNAMIC-LINKER-OPTION: "{{.*}}ld{{(\.lld)?(\.exe)?}}"
 ! RDYNAMIC-LINKER-OPTION-SAME: "-export-dynamic"
 
 ! For MSVC, adding -static does not add any additional linker options.

flang/test/Driver/isysroot.f90

@@ -8,7 +8,7 @@
 ! RUN: %flang -### --target=aarch64-linux-gnu -isysroot /path/to/sysroot \
 ! RUN:        %s 2>&1 | FileCheck %s --check-prefix=CHECK-LINUX
 
-! CHECK-DARWIN: "{{.*}}ld{{(64)?(\.lld)?}}" {{.*}}"-syslibroot" "/path/to/sysroot"
+! CHECK-DARWIN: "{{.*}}ld{{(64)?(\.lld)?(\.exe)?}}" {{.*}}"-syslibroot" "/path/to/sysroot"
 ! Unused on Linux.
 ! CHECK-LINUX: warning: argument unused during compilation: '-isysroot /path/to/sysroot'
 ! CHECK-LINUX-NOT: /path/to/sysroot