virtual memory exhausted: Cannot allocate memory while building btree_test.cc.o

### Describe the issue

```sh
..
..
[ 42%] Built target flags
[ 42%] Building CXX object absl/container/CMakeFiles/absl_btree_test.dir/btree_test.cc.o
virtual memory exhausted: Cannot allocate memory
make[2]: *** [absl/container/CMakeFiles/absl_btree_test.dir/build.make:63: absl/container/CMakeFiles/absl_btree_test.dir/btree_test.cc.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:4031: absl/container/CMakeFiles/absl_btree_test.dir/all] Error 2
make: *** [Makefile:141: all] Error 2
```

### Steps to reproduce the problem

```sh
cmake -DABSL_BUILD_TESTING=ON -DABSL_USE_GOOGLETEST_HEAD=ON -DCMAKE_CXX_STANDARD=14 ..
cmake --build . --target all
```

### What version of Abseil are you using?

master branch
c9c0fd5185067208e1cc4227d16122571762af39

### What operating system and version are you using?

Distributor ID: Debian
Description: Debian GNU/Linux 10 (buster)
Release: 10
Codename: buster

### What compiler and version are you using?

gcc (Debian 8.3.0-6) 8.3.0

### What build system are you using?

cmake version 3.13.4

### Additional context

system total memory is about 2000MB, no other process consume much memory.
While building btree_test.cc.o, in '$top' i saw VIRT & RES of process cc1plus counted up to 1800000 ~ 1900000 gradually, after which i got 'virtual memory exhausted'