Firefox Build Error: old-configure failed - firefox

Question

I'm trying to build Firefox(60.esr) from source. I followed the steps mentioned in Build Firefox on Windows. But it fails.
Method #1:
I followed all the steps mentioned in the Windows Build Instruction.
The Build process failed with error.
0:24.36 ERROR: Could not find LLVM/Clang installation for compiling stylo build-time
0:24.36 bindgen. Please specify the 'LLVM_CONFIG' environment variable
0:24.36 (recommended), pass the '--with-libclang-path' and '--with-clang-path'
0:24.36 options to configure, or put 'llvm-config' in your PATH. Altering your
0:24.36 PATH may expose 'clang' as well, potentially altering your compiler,
0:24.36 which may not be what you intended.
So, I tried method 2.
Method #2:
Since it was expecting LLVM/clang, I installed LLVM/Clang 6.0 and added ‘LLVM_CONFIG’ to the environment variable.
And then I executed mach build. Adding LLVM_CONFIG fixed the error which was caused in Method 1.
But the build failed again with error.
0:16.24 c:/Users/n182s826/mozilla/mozilla-central/old-configure: fork: Resource temporarily unavailable
0:18.59 m.AllocationBase 0x0, m.BaseAddress 0x607A0000, m.RegionSize 0x240000, m.State 0x10000
0:18.59 C:\mozilla-build\msys\bin\sh.exe: *** Couldn't reserve space for cygwin's heap (0x607A0000 <0xB80000>) in child, Win32 error 0
0:18.59 0 [main] sh 13328 sync_with_child: child 14220(0x3B8) died before initialization with status code 0x1
0:18.59 51 [main] sh 13328 sync_with_child: *** child state waiting for longjmp
0:18.59 c:/Users/n182s826/mozilla/mozilla-central/old-configure: fork: Resource temporarily unavailable
0:18.61 ERROR: old-configure failed
0:18.65 *** Fix above errors and then restart with\
0:18.65 "c:/mozilla-build/mozmake/mozmake.EXE -f client.mk build"
I even raised a request at Bugzilla. But I haven't found any solution.