Makefile improvements

- Add an "all" build target
- Fix build if libcuda.so is not on linker search path
- Do not assume that nvcc is available on $PATH
- Allow specifying CFLAGS and LDFLAGS when running make
- Allow passing non-standard CUDA build locations to make

Suggested usage if CUDA is installed in a non-standard location,
say, /playpen/jbakita/CUDA/cuda-archive/cuda-12.2:

make CUDA=/playpen/jbakita/CUDA/cuda-archive/cuda-12.2

1 files changed, 4 insertions, 4 deletions

diff --git a/README.md b/README.md
index c3f87c4..f4d7cd1 100644
--- a/README.md
+++ b/README.md
@@ -29,10 +29,10 @@ To build, ensure that you have `gcc` installed and access to the CUDA SDK includ
 make libsmctrl.a
 ```
 
-If you see an error that the command `nvcc` was not found, `nvcc` is not available on your `PATH`.
-Correct this error by explictly specifying the location of `nvcc` to `make`, e.g.:
+If you see errors about CUDA headers or libraries not being found, your CUDA installation may be in a non-standard location.
+Correct this error by explictly specifying the location of the CUDA install `make`, e.g.:
 ```
-make NVCC=/playpen/jbakita/CUDA/cuda-archive/cuda-10.2/bin/nvcc libsmctrl.a
+make CUDA=/playpen/jbakita/CUDA/cuda-archive/cuda-10.2/ libsmctrl.a
 ```
 
 For binary backwards-compatibility to old versions of the NVIDIA GPU driver, we recommend building with an old version of the CUDA SDK.
@@ -41,7 +41,7 @@ For example, by building against CUDA 10.2, the binary will be compatible with a
 Older versions of `nvcc` may require you to use an older version of `g++`.
 This can be explictly specified via the `CXX` variable, e.g.:
 ```
-make NVCC=/playpen/jbakita/CUDA/cuda-archive/cuda-8.0/bin/nvcc CXX=g++-5 libsmctrl.a
+make CUDA=/playpen/jbakita/CUDA/cuda-archive/cuda-8.0/ CXX=g++-5 libsmctrl.a
 ```
 
 `libsmctrl` supports being built as a shared library.