external/otf2/CMakeLists: Do not pass LDFLAGS from env (#1010)

When configuring the otf2 dependency, CFLAGS, CXXFLAGS, CC and CXX are
explicitly specified, but LDFLAGS is not.  As a consequence, LDFLAGS is
picked up from the environment (if set).  In some build configurations,
the LDFLAG from the environment is not compatible with the rest of the
compiler/linker configuration options specified in CMakeLists.txt,
resulting in the configure script failing.

This patch make sure to specify an empty LDFLAGS when configuring otf2
build to avoid such issues.

Bug: SWDEV-477693

external/otf2/CMakeLists.txt

@@ -59,7 +59,7 @@ externalproject_add(
     PATCH_COMMAND
         ${CMAKE_COMMAND} -E env CC=${CMAKE_C_COMPILER} CXX=${CMAKE_CXX_COMPILER}
         <SOURCE_DIR>/configure -q --prefix=${_otf2_root} CFLAGS=-fPIC\ -O3\ -g
-        CXXFLAGS=-fPIC\ -O3\ -g PYTHON=: SPHINX=:
+        CXXFLAGS=-fPIC\ -O3\ -g LDFLAGS= PYTHON=: SPHINX=:
     CONFIGURE_COMMAND ${MAKE_COMMAND} install -s
     BUILD_COMMAND ""
     BUILD_BYPRODUCTS "${_otf2_build_byproducts}"