[compiler-rt] Use LLVM_ENABLE_RUNTIMES instead of LLVM_ENABLE_PROJECTS in the symbolizer

[ldionne]

Summary

This was originally part of 176db3b3ab25 (D132324) which was reverted in
342e0ebd0b74 because it caused CI instability. This change is required
for compiler-rt to stop depending on the deprecated way of building libc++.

[Ericson2314]

Code looks good.

I don't recall build failures emails mentioning the symbolizer, so hopefully it doesn't cause CI problems too!

[ldionne]

@vitalybuka I should have pinged you on this, I just saw 89476dbca18c20edfa02548061cdee77d4808427!

[ldionne]

I guess this doesn't have a purpose anymore. @vitalybuka thanks for cleaning it up!

compiler-rt/lib/sanitizer_common/symbolizer/scripts/build_symbolizer.sh

 CC=$CC CFLAGS="$FLAGS" RANLIB=/bin/true ./configure --static
 make -j${J} libz.a
 
 # Build and install libcxxabi and libcxx.
 if [[ ! -d ${LIBCXX_BUILD} ]]; then
   mkdir -p ${LIBCXX_BUILD}
   cd ${LIBCXX_BUILD}
   LIBCXX_FLAGS="${FLAGS} -Wno-macro-redefined"
-  PROJECTS=
+  RUNTIMES=
   if [[ ! -d $LLVM_SRC/projects/libcxxabi ]] ; then
-    PROJECTS="-DLLVM_ENABLE_PROJECTS='libcxx;libcxxabi'"
+    RUNTIMES="-DLLVM_ENABLE_RUNTIMES='libcxx;libcxxabi'"
   fi
   cmake -GNinja \
-    ${PROJECTS} \
+    ${RUNTIMES} \
     -DCMAKE_BUILD_TYPE=Release \
     -DCMAKE_C_COMPILER=$CC \
     -DCMAKE_CXX_COMPILER=$CXX \
     -DCMAKE_C_FLAGS_RELEASE="${LIBCXX_FLAGS}" \
     -DCMAKE_CXX_FLAGS_RELEASE="${LIBCXX_FLAGS}" \
     -DLIBCXXABI_ENABLE_ASSERTIONS=OFF \
     -DLIBCXXABI_ENABLE_EXCEPTIONS=OFF \
     -DLIBCXXABI_ENABLE_SHARED=OFF \